Switch from Microsoft 365 Business to Posteo: step by step

How to move your mail, contacts and address from Microsoft 365 Business to Posteo without losing anything. Most moves take an evening to set up, then a few weeks of forwarding.

Moving fromGmailOutlook.comiCloud MailProton MailFastmailTutamailbox.orgPosteoZoho MailGoogle WorkspaceMicrosoft 365 BusinessMailfenceStartMailRunboxAnother providerMoving toGmailOutlook.comiCloud MailProton MailFastmailTutamailbox.orgPosteoZoho MailGoogle WorkspaceMicrosoft 365 BusinessMailfenceStartMailRunboxAnother provider

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1. Before you start

   • Check where your address lives. Microsoft 365 Business runs on your own domain, like you@yourname.co.uk, so your address comes with you: you'll change a few DNS settings.
   • Check the space you need. See how much mail you have in Microsoft 365 Business, and compare it with Posteo's plans (the cheapest is Posteo, €1 a month, with 4 GB).
   • Read the small print. Posteo's page covers exporting, cancelling and refunds under "Before you sign up".

2. Open your Posteo account

   Sign up on Posteo's website (No, €1 a month from the start), and turn on two-step sign-in straight away. You'll find the link on Posteo's page: Posteo.

3. Bring your mail across

   Use Posteo's importer. Posteo's free migration service copies up to three accounts, with their folders, from any provider that allows IMAP. Open Settings, then My account, then Posteo migration service. Posteo's guide ↗

   Your old mail stays where it is while it's copied, so nothing is lost if you need to start again.

4. Move your contacts and calendar

   Export your contacts as a .vcf file and each calendar as an .ics file from Microsoft 365 Business, then import them into Posteo. Most providers have both options in their contacts and calendar settings. Posteo can copy your address book automatically from Gmail, iCloud, Microsoft, Yahoo, AOL, GMX and WEB.DE. Posteo's guide ↗

5. Check everything arrived

   • Compare the number of emails in each folder on both sides.
   • Send a test email to your new address from another account, and reply to it.
   • Check that mail forwarded from Microsoft 365 Business is arriving, and isn't going to spam.

6. Close Microsoft 365 Business, when you're ready

   Wait at least a month, until nothing new arrives there. On a free account you can leave it open with forwarding on instead. Before you close a paid account, download a last copy of your mail.

   From Microsoft 365 Business's page: Microsoft 365 Business.

I checked the providers' help pages on 24 October 2026. Menus move, so if a step doesn't match what you see, tell me and I'll update it.

Moving to Posteo from somewhere else? Gmail to Posteo · Outlook.com to Posteo · iCloud Mail to Posteo · Proton Mail to Posteo · Fastmail to Posteo · Tuta to Posteo · All switching guides