Migrating means moving mailboxes, calendars, contacts and files to another operator, then getting new mail to arrive in the right place. It does not mean reproducing Teams, advanced Excel or Power Automate. A successful migration starts with the list of what employees actually do in Microsoft 365.
Microsoft 365 is not a piece of software; it is a set of services linked by the same directory. A team that believes it “only uses email” often stores its attachments in OneDrive, shares a SharePoint folder with a client and organises its meetings in Teams. The scope is therefore read from usage, not from the list of licences.
Over a sample of teams, record the week’s usage: email, OneDrive, SharePoint, Teams (conversations, files, meetings), Excel with macros, Power BI, forms, connected business applications. Classify them.
One technical detail often changes the scope: files posted in a Teams channel are stored in SharePoint, and those sent in a private chat are stored in the sender’s OneDrive. Migrating “the files” without looking at Teams therefore leaves out part of the body of content, or copies it without its context.
If the third column is the core of the business, migrating the email service may still make sense (for example, a filter placed in front of Microsoft 365), but replacing the suite does not. Saying so before the quote avoids a pointless project. The page Microsoft 365 compared with a sovereign solution sets out this threshold, and the guide to European alternatives compares the possible targets.
Take, by way of illustration, an industrial SME with two sites. Administration and sales staff live in email, the calendar and everyday files: they move across without difficulty. The engineering department, however, keeps its cost estimates in macro-enabled workbooks and tracks its production in Power BI. Replacing the whole suite would break that team’s working tool. The reasonable decision may be to migrate email and simple files, and to leave the engineering department what it needs. This choice is written down at the outset.
Steps 1 to 4 are invisible to employees and reversible: as long as the MX has not changed, mail continues to arrive in Microsoft 365. The MX is the DNS record that tells servers all over the world where to deliver mail for your domain. It is the only action that actually switches the flow, and it must come when everything else is ready.
The TTL (time to live) tells DNS resolvers how long they may keep the answer in memory. It is lowered in advance because a resolver that has read the old value keeps it until it expires: the short TTL only applies once the old cache has run out. Take advantage of this change to remove any secondary MX records still pointing to Microsoft 365: a sending server that cannot reach the primary MX tries the next ones, and would then deliver to the old platform.
Closing down sending matters just as much. Microsoft 365 still considers itself responsible for your domain: an employee still connected to the old Outlook who writes to a colleague has their message delivered inside the tenant, without going through the MX. The message exists, but in a mailbox that nobody reads any more.
The details of a cutover without a gap in mail are in migrating an email service without interruption. The operational list is the checklist.
Shared mailboxes and delegations. A shared mailbox is copied like any other. The permissions, however, do not follow: full access, send as, send on behalf, calendars delegated to an assistant. They are recreated on the target and tested with the person who uses them, not with the administrator.
Archives and litigation hold. Online archives are a space separate from the primary mailbox. A copy tool that does not explicitly target them ignores them. A mailbox under litigation hold generally meets an obligation: before closing it, check with the person who requested it how that obligation will be met afterwards (copy to the target, retained export, or temporary retention).
Autodiscover. Outlook finds the server settings through the autodiscover DNS record. If it still points to Microsoft, a reconfigured workstation may keep looking for the old service or repeatedly ask for a password. This record is changed on the day of the cutover, along with the MX.
SPF, DKIM, DMARC. These records allow recipients to verify that your mail is legitimate. A domain must publish only one SPF record; during the transition, it authorises both platforms, then Microsoft is removed. DKIM works by selector: the new platform’s key can be published alongside the old one, before the cutover. DMARC requires at least one of the two checks to be aligned with the sender’s domain: if the target is not yet authorised, correspondents who apply a strict policy reject your messages.
On a Zimbra, BlueMind or equivalent email service, Outlook for Windows often reconnects via Exchange ActiveSync or the protocols provided by the software vendor. The webmail changes. Teams shortcuts do not come back. Files opened in the browser go through the target’s online editor (OnlyOffice, Collabora, or another suite), whose level of compatibility with complex workbooks must be tested on your files, not on a demo.
For Outlook, creating a new profile is safer than modifying the old one: the local cache keeps references to the Microsoft server, and the mix produces duplicates or ghost folders. On a mobile device, the rule is the same: delete the account, then recreate it. The first load of a large mailbox takes time: warn the users concerned.
Announce this difference before the cutover. The projects that fail are those where management sold “the same thing, but European”.
No. The domain remains yours: only the server that receives it changes. Correspondents continue to write to the same addresses, and the MX change is invisible to them if it is well prepared.
It is possible, but it is long-term coexistence, not a migration. The two platforms then share the same domain: one receives the mail and relays to the other the addresses it does not host. This has to be designed, documented and maintained. For an engineering department that must keep Excel and Power BI, it is sometimes the right choice.
Not necessarily. Some companies bring over everything, others bring over the useful years and archive the rest in a retained export. The choice depends on your retention obligations and on the copy time you are willing to pay for. It is written into the quote.
They do not migrate. A European solution offers other video conferencing or instant messaging tools, but the Teams history does not follow. For Power BI, you need either another analytics tool or to keep the licences concerned.
When the check sample is satisfactory, when no flow uses it any longer and when the necessary exports have been archived. Before cancelling, check in your contract what Microsoft retains after the end of the subscription and for how long: that is the date to note.
Klytic can take on email, documents (dedicated Nextcloud instance, with sharing, online editing alone or with others and version history), video conferencing, CRM and telephony, together or separately. The email service is based on Zimbra, published by Synacor (United States), hosted in Klytic’s email architecture, in a dedicated instance or on the client’s premises, and always operated by Klytic. It is accessible via the web, via email clients, on mobile, over EAS and over EWS. Hosting is provided in any geographical area corresponding to the applicable jurisdiction, subject to the availability of the required services, for example in Europe or Mauritius, or on the customer’s servers. See hosting and sovereignty.
For email, advisory support is free of charge, and Klytic guarantees that no email is lost. Migration carried out by Klytic is quoted on request, after the inventory. Klytic can also migrate only the filter (MTA in front of Microsoft 365) when the suite has to stay. Klytic does not replace Teams, advanced Excel or Power BI.
The cost is built from this inventory. The page how much a migration costs explains the cost items, without fictitious figures. Subscriptions are on the Pricing page; for a specific project, use the quote request.
This page describes a method. The result depends on the volume, the archives and the uses that do not leave Microsoft 365.
Accessed in October 2026.
Free advice, no email lost. A migration carried out by Klytic is quoted after an inventory.
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