Migrate from IONOS to Microsoft 365: The Steps to Follow

IONOS email (formerly 1&1) is fine for small volumes, but many companies want the power of Microsoft 365: Outlook, Teams, OneDrive and Office in one place. The classic fear is losing email history, or cutting off delivery at the wrong moment. Rest assured: by following the order backup → IMAP migration → MX cutover → verification, the transition happens cleanly, with no data loss.

What gets migrated — and why leave IONOS

A successful migration accounts for everything attached to the accounts, not just the messages:

• Email: inbox, folders, sent items, drafts and archives, with their folder tree.
• Contacts: each user's address book, exported from the IONOS webmail.
• Calendars: appointments and recurring meetings.
• Files: documents to move to OneDrive (personal) or SharePoint (team).

Companies leave IONOS for larger mailboxes, centralized administration, native Outlook and Teams integration, and mail that's better protected against spam and spoofing. It's also a chance to unify productivity and email under a single license.

Step 1 — Backup, audit and inventory

Before any DNS change, take stock:

• Back up each mailbox: in Outlook connected to IONOS, a PST export (File → Open & Export → Import/Export) is a complete safety net.
• List mailboxes, aliases and forwards and measure the volume to estimate transfer time.
• Note the IONOS IMAP settings (server such as imap.ionos.com, port 993 SSL).
• Check DNS: MX, SPF, DKIM and TTL records. Lower the MX TTL to 300 seconds a few days before the cutover.

Step 2 — Provision the Microsoft 365 tenant

Create the Microsoft 365 tenant, add and verify your domain (Microsoft provides a TXT record), then create the users and assign licenses. Don't change the MX yet: the mailboxes are ready but empty, mail keeps arriving on IONOS, and you prepare the transfer without stress.

Step 3 — Migrate email (IMAP migration)

Since IONOS exposes IMAP, the reference method is the IMAP migration in the Microsoft 365 Exchange admin center:

• Create an IMAP migration endpoint pointing to the IONOS server (imap.ionos.com, port 993 SSL).
• Provide a mapping file (CSV) linking each source address to the target Microsoft 365 mailbox and its password.
• Start the batch: Microsoft copies email in the background, without touching the incoming mail that stays on IONOS.

For a single mailbox, importing the PST you exported in step 1 into the new mailbox works just as well. Keep in mind that IMAP migration transfers email but not contacts or calendars — those are handled separately.

The secret to a zero-downtime switch: copy everything while the old mail system is still running, and only change the MX once the copy is finished.

Step 4 — Contacts, calendars and files

Export contacts (CSV/vCard) and calendars (.ics) from the IONOS webmail, then import them into Outlook / Microsoft 365. For files, move documents to OneDrive (personal data) or SharePoint (team data): copy the folders and let the OneDrive sync client finish the upload.

Step 5 — Cut over DNS/MX with no downtime

Once the initial copy is done, change the DNS records at IONOS (or your registrar):

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

Thanks to the lowered TTL, propagation is fast. During coexistence, some mail may still arrive on IONOS; run a delta sync (another IMAP pass) to pull in messages received between the initial copy and the cutover.

Step 6 — Verification and client settings

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

Common pitfalls

• Rate limits: IONOS caps simultaneous IMAP connections; spread out the batches to avoid errors.
• Duplicates: after the cutover, only run a delta sync, never a full migration.
• Sharing permissions: access rights on shared folders don't transfer automatically — recreate them on the Microsoft side.
• Recurring calendars: some recurring meetings can shift; check them after import.
• Cancelling IONOS 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 IONOS 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 IONOS to Microsoft 365 for you

Describe your migration in one sentence — "migrate my IONOS mailboxes to Microsoft 365" — and the AI does the rest: it backs up and audits the mailboxes, 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.