Migrate from OVH to Microsoft 365: Email, Calendars and Files

Many companies leave OVHcloud email plans — Exchange, Email Pro or Zimbra (MX Plan) — for Microsoft 365, to bring mail, Teams and Office together. The worry is always the same: losing years of history, or cutting off mail in the middle of the day. Good news: with the right method, the switch happens with no data loss and no visible interruption for the people who write to you.

What gets migrated — and why people leave OVH

An email migration covers far more than messages alone. You need to think about everything tied to the accounts:

• Email: inbox, folders, sent items, drafts and archives, with their full folder tree.
• Contacts: each user's personal address book and, where relevant, shared lists.
• Calendars: appointments, recurring meetings and shared calendars.
• Files: documents kept on an OVH space (web hosting, NAS) that you want to move to OneDrive or SharePoint.

The reasons are familiar: put mail alongside Word, Excel, Teams and OneDrive under a single licence, get larger mailboxes, and centralise administration. Moving from Email Pro or Zimbra to a full Microsoft environment also simplifies day-to-day work for teams.

Step 1 — Audit and inventory before touching DNS

No successful migration starts with the technical bit. It starts with a precise inventory:

• List every mailbox to migrate (named accounts, shared ones like contact@, aliases, forwards).
• Measure the size of each mailbox: this drives transfer time and the risk of rate limiting.
• Identify your exact OVH plan (Exchange, Email Pro or Zimbra MX Plan): the IMAP connection mode and server settings depend on it.
• Check the domain and DNS: note who manages the DNS zone, the current MX records, SPF, DKIM and above all the TTL. Lower the MX TTL (e.g. to 300 seconds) a few days before the cutover so the change propagates quickly.

Step 2 — Provision the Microsoft 365 tenant

On the target side, create the Microsoft 365 tenant, add and verify your domain (Microsoft supplies a TXT verification record), then create users and assign licences. At this point, do not change the MX yet: the new mailboxes are ready but empty, and mail keeps arriving at OVH. That lets you prepare the transfer calmly.

Step 3 — Migrate email (IMAP or PST)

Because OVH plans expose IMAP, the go-to method is the IMAP migration in the Microsoft 365 Exchange admin center:

• Enter the OVH IMAP server (for example ssl0.ovh.net for Exchange/Email Pro), port 993 over SSL.
• Provide a mapping file (CSV) linking each source address to its target Microsoft 365 mailbox and password.
• Start the batch: Microsoft copies the email in the background, without touching incoming mail, which still lands at OVH.

For small volumes or a single mailbox, a PST export from Outlook (File → Open & Export → Import/Export) followed by an import into the new mailbox is a simple alternative. Note that IMAP migration moves email but not contacts or calendars: those are handled separately.

The secret to a zero-downtime cutover: copy everything while the old mailbox is still running, and only change the MX once the copy is complete.

Step 4 — Contacts, calendars and files

Contacts and calendars don't travel over IMAP. The most reliable path is to export contacts as CSV/vCard and calendars as .ics from the old webmail (or from Outlook connected to OVH), then import them into Outlook / Microsoft 365. For files, move documents to OneDrive (personal data) or SharePoint (team data): mount the source space, copy the folders, and let OneDrive sync finish the upload.

Step 5 — Cut over DNS/MX with no downtime

Once the initial copy is done, change the DNS records at OVH (or your registrar) to point to Microsoft:

• MX to your-domain.mail.protection.outlook.com.
• autodiscover CNAME to autodiscover.outlook.com.
• SPF updated with include:spf.protection.outlook.com, then enable DKIM on the Microsoft side.

Thanks to the lowered TTL, propagation is fast. During a few hours of coexistence, some mail may still arrive at OVH; run a delta sync (a fresh IMAP pass) to bring over messages received between the initial copy and the cutover.

Step 6 — Verify and set up clients

Check that no folder is missing, send and receive a test email, then reconfigure clients: in Outlook, recreate the profile with the Microsoft 365 account (autodiscover does the rest); on mobile, remove the old OVH account and add the Microsoft one. Also review signatures, rules and forwards.

Common pitfalls

• Rate limits: OVH and Microsoft cap simultaneous IMAP connections. Stagger the batches to avoid errors.
• Duplicates: after the cutover, don't rerun a full migration, only a delta sync, or you'll duplicate messages.
• Sharing permissions: access rights on shared folders don't carry over automatically; recreate them on the Microsoft side.
• Recurring calendars: some recurring meetings or invites can shift; check them after import.
• Cancelling OVH too early: only close the source plan after several days of confirmed operation on Microsoft 365.

How much it costs: Yuna7 vs an IT contractor

Having a contractor migrate OVHcloud to Microsoft 365 often costs several hundred dollars, with quotes and lead times. Yuna7 automates the switch and you only pay for what's actually used — you can even try it free.

Let Yuna7 migrate OVHcloud to Microsoft 365 for you

Describe your migration in one sentence — "migrate my OVH mailboxes to Microsoft 365" — and the AI does the rest: it audits the mailboxes and DNS, provisions the tenant, transfers email, contacts, calendars and files, cuts the MX over at the right moment and verifies nothing is missing. You only approve the sensitive steps. Far cheaper than a technician, and launched in minutes.