Microsoft 365 vs grommunio: when keeping Outlook on self-hosted mail makes sense
If you are facing an Exchange or Microsoft 365 renewal, a data residency rule, or a wish to keep Outlook while changing the server behind it, grommunio is worth evaluating because it speaks MAPI/HTTP, EWS and ActiveSync, so existing Outlook and mobile clients can stay in place. Microsoft 365 remains the better fit where a Microsoft-operated cloud and the full Office suite are the requirement, and grommunio does not replace that suite. The decision turns on three things: how much hosting control your rules actually demand, which mail and collaboration surfaces your users rely on day to day, and whether your team has the operating capacity to run an appliance-based groupware server with its own patching, backup and directory integration.
Start by listing the Outlook features your users depend on, such as shared mailboxes, delegation, public folders, out-of-office rules, room booking and mobile sync policies, and test each one against a grommunio pilot with the same client versions you run today. Confirm with the vendor which Exchange features are covered by MAPI/HTTP, EWS and ActiveSync and which are not, because clients often fail on edge cases rather than basic send and receive. Also confirm that grommunio can use the same LDAP or Active Directory as your current environment, since the documented Exchange migration path depends on it.
Operating capacity is the factor most often underestimated. grommunio ships as an appliance built on openSUSE, delivered as ISO or OVA images with a setup wizard, and it also documents manual and container installation. Your team pays for the infrastructure, the staff time to patch and monitor it, and the backup and restore testing that keeps mail recoverable. Ask grommunio or its certified partner what support tier, upgrade path and recovery objectives come with each license, and compare those with the Exchange Server Subscription Edition or Exchange Online service you would otherwise run.
Which option fits which scenario
This table matches common buyer situations to the option that usually fits better, with the reason tied to a researched fact. Read each row against your own mail volume, user count, client mix and hosting rules, because the right answer depends on which constraint dominates.
| Scenario | Better fit | Why |
|---|---|---|
| Keep Outlook clients with mail in your own data center or private cloud | grommunio | grommunio supports MAPI/HTTP, EWS and Exchange ActiveSync, and its FAQ says existing Outlook clients can stay in use. |
| Microsoft 365 with Teams and desktop Office as a fixed standard | Microsoft 365 | grommunio bundles chat, video and files as forks of upstream projects, but it does not replace desktop Office apps or the Teams client itself. Confirm any integration gap with the vendor. |
| Regulated or EU-hosted mail where your team operates the servers | grommunio | Gromox is AGPL-3.0 and runs on servers you control, and grommunio is positioned as a European platform. Your operations team takes on patching, backup and uptime. |
| Small team of up to 5 users with no need for vendor support | grommunio Community package | The free Community package covers up to 5 users without manufacturer support, so budget for internal administration time instead of a license. |
| Team of 6 to 49 users that wants paid support | grommunio Basic or Plus | Per-user tiers start at 6 users on the pricing page, with Basic at 1.99 euros and Plus at 3.99 euros per user per month. Licenses are sold through certified partners. |
| Very large mailboxes or heavy eDiscovery and legal hold needs | Microsoft 365 or a dedicated archive | Purview eDiscovery exports to PST or .msg, but export requires an E3 or E5 license and packages expire after 14 days. grommunio does not document an equivalent case management feature, so confirm this with the vendor. |
| Organization above 1,000 users wanting custom contracts | Evaluate grommunio Enterprise or Microsoft 365 | Enterprise pricing starts at 1,000 users and is quoted individually. Compare the written quote against your existing Exchange and eDiscovery costs. |
How grommunio maps to Exchange and Outlook
Gromox is the server component that does the mail work in grommunio, and it is the part that decides whether existing Outlook clients keep working. grommunio states that organizations can keep their Microsoft Outlook clients through MAPI/HTTP, EWS and Exchange ActiveSync support. Gromox also implements RPC/HTTP (Outlook Anywhere), IMAP, POP3 and an SMTP local delivery agent, and it can scale out across multiple hosts. This matters most when desktop Outlook is the daily client for a large user base and you cannot retrain people or change clients on the same weekend as the server move.
- MAPI/HTTP and RPC/HTTP: These are the transports desktop Outlook uses to reach an Exchange-style server. Confirm them with your own Outlook build, profile setup and autodiscover configuration.
- Exchange Web Services: Needed by third-party tools, add-ins and some line-of-business applications that call EWS directly. Inventory these before cutover.
- IMAP and POP3: Useful for devices and legacy clients that do not speak the Exchange protocols, but they do not carry full Exchange semantics such as shared calendars or delegation in the same way.
- Scale-out: Gromox can run across multiple hosts, which affects sizing and high availability design. Ask grommunio how this is deployed for your user count.
- Coexistence: Plan mail routing and autodiscover during the transition period, and test sending and receiving across both systems before users move.
Before committing, run an Outlook test matrix covering your client versions, add-ins and shared mailboxes against a grommunio test instance.
Mobile devices are where many Exchange deployments depend on ActiveSync, and grommunio addresses this with grommunio-sync. According to grommunio's documentation, this component provides Exchange ActiveSync for native iOS and Android clients. Mobile mail, calendar and contact sync is the workload most often broken by a server change, because device policies, certificates and push behavior vary by platform. This tab matters if you have a large mobile fleet, managed device policies that reference ActiveSync, or executives who rely on the native mail app.
- Native clients: grommunio-sync targets the native iOS and Android mail apps. Test each OS version in your fleet, not only the latest release.
- Device policies: Check whether your mobile device management product applies ActiveSync-based policies and how those policies map to the grommunio configuration.
- Certificates and endpoints: Mobile clients are sensitive to TLS chains and hostnames. Verify the published endpoint before the migration window.
- Push and delivery timing: Measure delivery latency and battery impact on test devices rather than assuming parity with Exchange.
- Remote wipe and selective wipe: Confirm that these work for your MDM workflow, since they are often a compliance requirement.
Ask grommunio to document the supported ActiveSync feature set against your current Exchange policy export before you schedule device migration.
Calendars and contacts reach users through several paths, and grommunio separates them from the core mail server. According to grommunio's introduction, grommunio-dav provides CalDAV and CardDAV, which serve clients that use open standards instead of Exchange protocols. Meeting invitations and free/busy data still depend on how Outlook and mobile clients talk to the server, so this tab matters if you use non-Microsoft calendar clients, Linux desktops or shared resource calendars.
- CalDAV and CardDAV: These cover calendar and contact access for standards-based clients. Confirm which clients your staff actually use before assuming coverage.
- Shared and resource calendars: Room and equipment booking, delegation and shared mailboxes are often the hardest part to reproduce. Test them explicitly.
- Free/busy and invitations: Verify that meeting invitations and availability lookups behave correctly between Outlook users, mobile users and CalDAV clients.
- Directory integration: grommunio is documented as compatible with LDAP and Active Directory. Confirm how contact lists and global address lookup are populated.
- Data migration: Contacts and calendars move through the PST export path, so verify item counts and recurring meeting exceptions after import.
Build a list of calendar scenarios your business depends on and test each one before users rely on the new system.
The wider grommunio suite includes chat, video, files and office components. According to grommunio's documentation, these are forks of upstream projects such as Nextcloud, Jitsi and ONLYOFFICE. That lineage helps you judge the feature set, but it does not make them one-to-one replacements for Teams, SharePoint or desktop Office. This tab matters if you plan to retire Teams, SharePoint or Office licenses along with Exchange. Treat these components as separate workloads that need their own requirements, testing and sign-off.
- Chat and meetings: The chat and meet components derive from upstream projects. Compare channel, guest access, retention and meeting-recording behavior with your Teams usage.
- Files and sharing: The files component is a fork of Nextcloud. Map SharePoint sites, OneDrive libraries and sharing policies to it explicitly, since these do not map automatically.
- Office editing: The office component is a fork of ONLYOFFICE. Test .docx, .xlsx and .pptx fidelity with your templates and macros. Desktop Office features are not assumed to carry over.
- Integration depth: Check how chat, files and calendar connect to each other and to your identity provider.
- Support boundary: Confirm which components grommunio supports directly and which depend on upstream behavior.
Do not assume that Teams, SharePoint or desktop Office have a one-to-one equivalent in grommunio. Test these workloads with real documents, meetings and permissions before deciding what to retire.
Capabilities side by side
This table maps the Microsoft 365 workloads a mailbox owner touches daily against what grommunio documents and what still needs confirming. Where grommunio's documentation is silent, the cell says so, and the buyer should confirm the point with grommunio before committing to a migration plan.
| Capability | Microsoft 365 | grommunio |
|---|---|---|
| Mail server | Exchange Online, a cloud service Microsoft operates | Gromox, AGPL-3.0, self-hosted, can scale out across multiple hosts |
| Outlook client support | Native Outlook desktop, web and mobile clients | Existing Outlook clients kept through MAPI/HTTP, EWS and Exchange ActiveSync support |
| EWS and ActiveSync | Supported by Exchange Online | Gromox implements Exchange Web Services; grommunio-sync provides ActiveSync for native iOS and Android clients |
| Calendar and contacts | Outlook calendar and contacts through Exchange Online | Calendar and contacts through Exchange protocols; CalDAV and CardDAV via grommunio-dav. Confirm shared-calendar and room behavior with grommunio |
| Chat | Microsoft Teams chat | Chat component forked from upstream projects; confirm channel, guest and retention behavior with grommunio |
| Video | Microsoft Teams meetings | Meet component forked from Jitsi; confirm scale, recording and federation with grommunio |
| Files and document editing | OneDrive and SharePoint with Office for the web and desktop apps | Files component forked from Nextcloud; office component forked from ONLYOFFICE. Confirm file-format fidelity and co-authoring limits |
| Identity integration | Microsoft Entra ID, with hybrid sync from on-premises Active Directory | Compatible with LDAP and Active Directory; grommunio must use the same directory as Exchange during migration |
| Hosting models | Multi-tenant cloud, with Exchange Server and SharePoint Server options for on-premises | Self-hosted appliance on openSUSE as ISO or OVA; manual and container installation also documented |
| Licensing model | Per-user Microsoft 365 subscriptions | Free Community package up to 5 users without manufacturer support; paid Basic, Plus and Business tiers per user per month from 6 users; Enterprise custom from 1,000 users. Sold through certified partners only |
| eDiscovery and retention | Purview eDiscovery; PST and native export requires E3 or E5 | Not documented in the sources reviewed. Ask grommunio for legal hold, search and export tooling before relying on it |
Where the mail data lives and who controls it
Moving mail from Microsoft 365 to grommunio changes who runs the servers, who holds the keys and who applies updates. The cards below cover the decisions that follow from that shift, from hosting and installation to licensing and compliance evidence.
Hosting and server ownership
With grommunio, mailboxes, MariaDB metadata and SQLite mailbox stores sit on servers your organization or your chosen hosting provider operates. Microsoft 365 keeps Exchange Online data in Microsoft's cloud under Microsoft's operating model. Confirm which data centers, regions and backup locations your own infrastructure team or hosting partner will use, and who holds administrative credentials for the hypervisor, the storage and the database.
Appliance delivery and setup
grommunio ships as an openSUSE-based appliance in ISO or OVA form, with a setup wizard for first configuration. The documentation also describes manual and container installation. The appliance route suits teams that want a fixed base image, while manual or container routes suit teams that already standardize on their own operating system build and configuration management. Decide early, because the choice affects patching, backup and upgrade procedures.
Identity integration with LDAP and AD
grommunio is compatible with LDAP and Active Directory, so existing user accounts and groups can drive mailbox access without a second directory. This matters most for the Exchange migration path, which requires grommunio to use the same LDAP or Active Directory as Exchange. Check how your directory schema, group nesting and password policy map to grommunio before cutover, and confirm how disabled accounts are handled so mailboxes do not stay live after an employee leaves.
Gromox scale-out across hosts
Gromox, the groupware server behind grommunio, can scale out across multiple hosts. That gives an architecture path for larger mailbox populations, but it also adds components to operate, monitor and back up. Ask for a documented topology for your user count, a plan for mailbox placement and failover, and a tested restore procedure. Do not assume that a scaled deployment carries the same support terms as the single-appliance Community package.
AGPL-3.0 licensing for internal use
Gromox is licensed under AGPL-3.0. Internal use of the software on your own servers carries no fee for the license itself, but the AGPL asks for source availability when you modify the program and make it available to users over a network. Legal teams should review whether any custom Gromox changes, connectors or hosted service offerings trigger those obligations, and should document the license position alongside the vendor support terms.
Compliance evidence and assessor roles
Mail retention, access logging, backup testing and change records all need evidence for an assessment. DeployOpen can plan, configure and document those controls on your grommunio deployment, and prepare the evidence set. Auditors and certification bodies issue any report or certification, and grommunio itself does not supply one through this comparison. Ask your assessor early which evidence they expect and which controls must be tested on your own environment.
How the grommunio parts fit together
Gromox is the server that answers every mail client, and it is the component your backup, capacity and troubleshooting plans should start from. It implements RPC/HTTP for Outlook Anywhere, MAPI/HTTP, Exchange Web Services, IMAP, POP3 and an SMTP local delivery agent, so Outlook on Windows, Outlook on the web-style clients and IMAP devices all reach the same mailbox store. Behind it, grommunio-sync provides Exchange ActiveSync for native iOS and Android clients, and grommunio-dav provides CalDAV and CardDAV for calendars and contacts. The practical consequence is that a client problem can sit in the protocol layer, the sync layer or the mailbox itself, so your support runbook should record which path each user's device takes before anyone changes a setting.
Storage is split in a way that shapes backup and restore. According to grommunio's documentation, MariaDB holds user metadata, while SQLite stores each individual mailbox. Backups therefore need to cover the database and the per-mailbox SQLite files together, and a restore test should confirm that a single mailbox can be recovered and that its metadata still matches the directory. Capacity planning is mostly about mailbox growth and disk I/O on the mailbox files, since many small SQLite stores behave differently from one large database. Ask grommunio, in writing, for its current guidance on backup consistency, scale-out across hosts (Gromox documents multi-host scale-out) and sizing per user, and confirm it against your own load test. The chat, meet and files components are forks of upstream projects and run beside the mail stack, so each needs its own update, backup and certificate plan.
The operator owns more than the product does. You are responsible for the directory, because grommunio must use the same LDAP or Active Directory as the source system during migration, and for the DNS records, certificates and mail flow that clients and external senders depend on, including autodiscover and the routing of inbound and outbound mail. You also own the client profiles: which Outlook builds, mobile devices and sync settings are approved, and how they are pushed. Before cutover, list each of these owners by name and confirm in the design document how DNS, certificate renewal and mail routing will be tested in your environment. Most of these items are unrelated to the vendor and will decide whether the migration holds.
Cost components on each side
Microsoft 365 and grommunio costs break into different parts: a per-user subscription on one side, and a license plus infrastructure and services on the other. The cards below separate one-time work from recurring spend so you can build a like-for-like comparison before asking for quotes.
Microsoft 365 subscription and add-ons
The recurring cost is the per-user Microsoft 365 plan, which you should price from your own enterprise agreement or reseller quote. Check which plan includes the Exchange Online features you use, then check add-ons separately. Purview eDiscovery export of mailboxes to PST is only available with an E3 or E5 license, so an export project can force a license tier change. Ask your account team which licenses your users hold today and what the renewal terms are.
grommunio license tier
Licenses are recurring and sold per user per month through certified partners. The grommunio pricing page lists a free Community package for up to 5 users without manufacturer support, Basic at 1.99 euros and Plus at 3.99 euros per user per month from 6 users, Business at 5.49 euros from 50 users, and custom Enterprise pricing from 1,000 users. Your tier depends on user count and on whether you need manufacturer support. Confirm with a partner whether the quoted price is per user, per month, and what the minimum seat count is.
Servers, virtual machines and hardware
This is a one-time build cost plus a recurring hosting cost. grommunio ships as an openSUSE-based appliance delivered as an ISO or OVA image, so you need hypervisor capacity or physical hosts that meet the vendor's sizing guidance. Gromox can scale out across multiple hosts, which raises the server count as your mailbox load grows. Ask your implementer for a sizing that covers peak concurrent ActiveSync and MAPI sessions, not only the average user count.
Storage and mailbox growth
Storage is the cost that grows fastest with time. In grommunio, MariaDB holds user metadata and SQLite stores individual mailboxes, so mailbox growth lands on the server disk and needs its own capacity plan. Compare the storage you pay for on Microsoft 365 with the disks, SAN or object capacity you buy yourself, including redundancy. Ask how archive and retention policies will be enforced on your storage.
Backup and disaster recovery
Backup is a recurring cost on both sides, but the responsibility differs. Microsoft 365 provides a hosted service, while with grommunio you must back up the appliance, the MariaDB data and the per-user SQLite mailboxes, and test restores. Budget for backup software or licenses, offsite copies and restore testing time. Confirm the recovery point and recovery time you need before choosing a backup product.
Migration and implementation services
This is mostly a one-time cost. Migration effort covers the Exchange export through the grommunio script, which exports mailboxes to PST and imports them over SSH, and the LDAP or Active Directory setup the script requires. Partner or DeployOpen implementation is quoted from a written scope that lists the mailboxes, clients, integrations and cutover plan. Ask for the scope, the acceptance criteria and whether the quote covers client reconfiguration for Outlook and mobile devices.
Ongoing operations and upgrades
Operations is the recurring cost that is easiest to underestimate. Someone must patch the appliance, apply release upgrades, monitor mail flow, manage spam and malware filtering, and handle user changes. Support from the manufacturer or a partner is a separate line that depends on your chosen tier. Ask for the upgrade path, who performs upgrades, and what support response commitments the quote includes.
Questions buyers ask before choosing grommunio
Can we keep Outlook on Windows and Mac with grommunio?
Yes, grommunio states that organizations can keep their existing Microsoft Outlook clients, because its server supports MAPI/HTTP, Exchange Web Services and Exchange ActiveSync. The server side is Gromox, which implements RPC/HTTP (Outlook Anywhere), MAPI/HTTP and EWS. Native iOS and Android clients connect through grommunio-sync. Before committing, confirm with grommunio which Outlook versions, add-ins and shared-mailbox or delegation features your users depend on are covered in your environment, and test them with a pilot group using your own client builds.
Does grommunio replace Teams and SharePoint?
Only partly. grommunio covers email, calendar, contacts, chat, video and files, and its chat, meet, files and office components are forks of upstream projects such as Nextcloud, Jitsi and ONLYOFFICE. That is a different feature set from Teams and SharePoint, so you should map each Teams channel, SharePoint library, site permission and workflow to a grommunio component and list the gaps. Features such as Microsoft's desktop Office apps, Teams apps and SharePoint lists may need a separate tool. Ask grommunio to confirm the exact feature coverage for your use cases.
How do we migrate mailboxes from Exchange to grommunio?
grommunio documents a script, exchange2grommunio.ps1, that exports each Exchange mailbox to PST with New-MailboxExportRequest and imports it on the grommunio server over SSH. The import pipes gromox-pff2mt into gromox-mt2exm, and the script logs successes and failures so a run can resume. The flow is per mailbox, so plan waves by user group and verify a sample of mailboxes after each wave. Calendars, contacts, delegations and folder permissions need separate checks, because the PST path does not guarantee that every object type maps cleanly.
What does the Exchange migration script require to run?
The script has three hard requirements:
- grommunio must use the same LDAP or Active Directory as Exchange, so users map to the same identities.
- It runs from an elevated Exchange Management Shell on Windows Server 2012 R2 or newer.
- A shared folder must be writable by Exchange and mountable on the grommunio server, so PST files can move between the two sides.
Check these before scheduling anything. Directory design, Exchange version and network paths between the Exchange host and the grommunio server often decide whether the migration can start in the planned window.
How long does a grommunio migration take, and what drives the effort?
No duration or effort figure for grommunio migrations was supplied, so ask grommunio and any implementation partner for a written estimate based on your environment. The main drivers are mailbox count and average mailbox size, the number of PST exports and imports you can run in parallel, network throughput between Exchange and grommunio, directory alignment, the number of shared and archive mailboxes, and how many custom client settings need retesting. Ask for the work split between pilot, waves, cutover and rollback, and who verifies each wave.
Can our own team run a grommunio migration without outside help?
It can be done in-house if your team has Exchange administration skills, Active Directory or LDAP knowledge, Linux administration for the grommunio appliance or container install, and a tested backup and rollback plan. grommunio ships as an appliance built on openSUSE, delivered as ISO or OVA with a setup wizard, and also documents manual and container installation. The skills gap is usually in verifying migrated data and running the cutover. Outside help can be scoped as a fixed engagement covering planning, testing, migration waves and documentation, which DeployOpen offers as fixed-scope work agreed in writing before work starts.
How do grommunio licensing tiers and partner sales affect the quote?
grommunio's pricing page lists a free Community package for up to 5 users without manufacturer support, Basic and Plus per user per month from 6 users, Business from 50 users, and custom Enterprise pricing from 1,000 users. The per-user prices are 1.99 and 3.99 euros for Basic and Plus, and 5.49 euros for Business. Licenses are sold only through certified partners, so the quote will come through a partner. Confirm the tier that matches your user count, which support level is included, whether migration help is in the price, and what renews each year.
What moving from Microsoft 365 to grommunio involves
The sequence moves mail, calendars and contacts from Exchange Online to grommunio in controlled waves while the identity source, client connections and retention obligations stay under your control. The end state is a grommunio server serving Outlook and mobile clients, with Microsoft 365 retired only once every retention need is met.
Confirm the directory and identity source
Before any mailbox moves, confirm which LDAP or Active Directory service holds users, groups and shared mailbox definitions, and that grommunio can read the same directory. The migration script requires grommunio to use the same LDAP or Active Directory as Exchange, so a mismatch here blocks everything that follows. Your identity team and the grommunio implementer sign off on the directory design, and the output is a written record of the directory source, the user and group mapping, and who owns each change.
Inventory mailboxes, shared mailboxes and devices
List every mailbox, shared mailbox, room or equipment resource, public folder, calendar delegation and distribution group, along with each user's mobile devices and Outlook profiles. Public folders and delegations often need separate handling because they are not simply exported with a user mailbox. Confirm with each business owner which mailboxes carry legal hold, retention or regulatory obligations. The output is an inventory with a named owner and migration wave for each item.
Decide what stays on Microsoft 365
Write down which workloads remain on Microsoft 365 after the mail move, such as Teams, SharePoint, OneDrive and desktop Office apps. grommunio bundles chat, video and files, but those components are forks of upstream projects and are not drop-in replacements for every Teams or SharePoint feature. Record the decision and the integration points that still depend on Microsoft 365, such as calendar free and busy lookups or application sign-in. The output is a signed scope document that the rest of the plan follows.
Export mailboxes to PST files
Export each mailbox to PST, either with New-MailboxExportRequest on the Exchange side as the grommunio script does, or through Microsoft Purview eDiscovery where your license supports it. Purview export requires a Microsoft 365 E3 or E5 license, and search export packages expire 14 days after creation, so download and stage packages promptly. Keep the export logs and checksums for each batch. The output is a complete set of PST files for every mailbox in the wave, stored on the shared folder the migration uses.
Run the migration in pilot waves
Start with a small pilot group of mailboxes, then move the remaining users in waves. The exchange2grommunio.ps1 script runs from an elevated Exchange Management Shell on Windows Server 2012 R2 or newer, with a shared folder writable by Exchange and mountable on the grommunio server. It imports each PST over SSH through gromox-pff2mt and gromox-mt2exm and logs successes and failures, so a failed run can resume without repeating completed items. Review the logs after each wave and resolve failures before the next wave starts. The output is a reconciled count of imported items per mailbox.
Cut over DNS, certificates and client profiles
Switch mail routing records, autodiscover entries and the TLS certificates presented by the grommunio endpoints so that Outlook, EWS and ActiveSync clients connect to the new server. Test MAPI/HTTP and Exchange ActiveSync from Windows Outlook, macOS, and iOS and Android devices in the pilot group before wider cutover. Confirm that mobile devices reprovision cleanly and that client profiles point to the new host. The output is a test record for each client type and a documented rollback path for DNS and certificates.
Retire the tenant after retention is met
Keep the Microsoft 365 tenant or its Exchange Online mailboxes in place until legal, regulatory and records obligations for the migrated data are confirmed as met in the new system. Do not remove licenses or delete mailboxes while holds or retention periods are open. Ask your compliance lead and legal counsel to sign off on what must be archived and where, and check the Microsoft 365 subscription terms for data removal timing. The output is a retirement approval that lists the systems, the archived data location, and the date each step was authorized.
What grommunio does not replace and what to plan for
grommunio replaces the Exchange side of Microsoft 365, not the whole suite. Outlook, mail, calendar and contacts map to Gromox, grommunio-sync and grommunio-dav, but Microsoft Teams, SharePoint, OneDrive and desktop Office are not one-to-one replacements. The chat, meet and files components are forks of upstream projects such as Nextcloud, Jitsi and ONLYOFFICE, so their feature sets, release cadence and admin controls will differ from the Microsoft products. This gap matters most if users rely on Teams channels, SharePoint document libraries with metadata, co-authoring inside desktop Office, or OneDrive sync for personal and shared folders. Before committing, run a pilot with real workflows from each department and ask grommunio, in writing, which features of each bundled component are supported, which are community-only, and how the forks are updated when upstream changes.
Advanced compliance is a separate planning item. Microsoft Purview eDiscovery is tied to Microsoft 365 licensing, and grommunio does not provide an equivalent hold, search and export workflow that you can assume is covered by the mail server alone. If you have legal hold, retention policy, journaling or litigation export obligations, define those requirements first and document which system will hold the archive, how searches are run, and who approves exports. Confirm with the vendor whether archiving, retention and audit logging are included in the edition you buy, and whether they are available in the Community package or only with paid tiers. Your own legal and records teams should sign off on the design, because the platform alone does not decide what your obligations are.
Plan the operating model before the cutover. Each bundled component adds patching, backup and monitoring work for your team, and the grommunio appliance is built on openSUSE, so your staff need to be comfortable with that platform. Decide early whether Teams and SharePoint users will move to a separate open-source product, such as a dedicated chat or file platform, or whether they will keep Microsoft 365 for those workloads during a transition. Ask for a written list of supported integrations with your existing Active Directory or LDAP, mobile clients, and Outlook versions, and confirm how the Exchange migration script behaves with your mailbox sizes and permissions before scheduling production waves.
How DeployOpen helps evaluate, implement and migrate
DeployOpen is a Chainscore Labs company that plans, implements, integrates, hardens, backs up and documents self-hosted open-source platforms inside your own cloud accounts, data centers or air-gapped networks. For Microsoft 365 against grommunio, that means working from your mail, calendar, directory and client requirements to a grommunio deployment you operate yourselves.
How we scope
- Inventory which Outlook clients, mobile devices and MAPI/HTTP, EWS or ActiveSync dependencies must keep working after cutover.
- Confirm LDAP or Active Directory integration, since the Exchange migration script depends on a shared directory.
- Agree the scope, deliverables and timelines in writing before any work starts, as most engagements are fixed-scope.
- Record which Microsoft 365 workloads grommunio will not replace, such as OneDrive, SharePoint and Teams, and how they are handled.
How we build
- Deploy grommunio in your environment using the appliance, container or manual install path that fits your hosting standards.
- Test Outlook, mobile and webmail access against a staging copy of your mailboxes before any user moves.
- Run mailbox migration trials through the PST export and import path, logging failures so each run can be resumed.
- Configure backups, TLS, access controls and monitoring for the mail server and its database and mailbox storage.
How we hand over
- Document the architecture, configuration, client settings and runbooks in a form your administrators can operate.
- Provide cutover and rollback steps, along with the user communication plan for Outlook profile changes.
- Walk your operations and security teams through backup restores, certificate renewal and patch procedures.
- Prepare control and evidence documentation for your compliance assessment, while independent auditors issue any formal opinion.
How we support
- Offer ongoing support, upgrades and continuous testing as a retainer after handover.
- Plan upgrades to new grommunio releases through staged testing before production rollout.
- Ask grommunio about its manufacturer support and licensing tiers, which are sold only through certified partners.
- Confirm with DeployOpen the scope of any retainer, including how mail server patches and client compatibility are handled.
