- IMAP server
- outlook.office365.com
- Port
- 993 · SSL/TLS
- Username
- full address
- Password
- app password
Outlook.com → Microsoft 365
Migrating Outlook.com to Microsoft 365
A personal Outlook.com mailbox and a corporate Microsoft 365 one sit on the very same host, outlook.office365.com, which makes the move look like a formality. In authentication terms they are two different worlds: the personal side still takes an app password, while the tenant usually has basic authentication disabled and needs OAuth.
- IMAP server
- outlook.office365.com
- Port
- 993 · SSL/TLS
- Username
- full address
- Password
- mailbox password
What breaks on this particular pair
- Same host, different rules. The source signs in with a Microsoft app password; the destination almost always goes through OAuth, with tenant admin consent.
- If basic auth is still enabled in the tenant a password will work — but Microsoft keeps retiring it, so it is not something to build on.
- Microsoft calls the junk folder Junk, not Spam. Manual mapping loses it more often than any other folder.
- Microsoft 365 caps the size of an incoming message (35 MB by default): anything larger shows up in the report as skipped.
FAQ
Common questions
Is a tenant administrator required?
If basic authentication is off in the tenant, yes: an admin grants the app the IMAP.AccessAsUser.All permission once. The personal Outlook.com side needs no consent.
Can calendars and contacts come along?
No. IMAP carries mail only; calendars and contacts are CalDAV and CardDAV and are exported separately.
Does the folder tree survive?
Yes, it transfers whole. Only the special names differ — Junk instead of Spam.
Does the mail stay in Outlook.com?
Yes, the default mode only copies.
Related routes
Other directions
Find out how big your mailbox is. It costs nothing.
Connect two servers, look at the size and decide. Or take the client and keep everything on your side.
Code on GitHub · built on imapsync · no sign-up