I have an e-mail service with associated domain name (say example.com) and 2GB of web space.

I use Microsoft Outlook, and until recently had about 10GB of e-mails stored locally (and on backups), coming from a total of 5 addresses (3 of which GMail) and the aforementioned paid custom domain name.

Recently, I changed my settings for my example.com e-mail from POP3 to IMAP. As a result, Outlook started telling me that folders were being synced and I now found all my 2GB on the server have been used up. It seems like Outlook started uploading ALL my e-mails (including the GMail ones, which I regularly moved to my folders in the 'example.com' Outlook inbox) to the server.

I would like to know if this is an exepcted behavior of the IMAP protocol, to automatically upload all my e-mails it finds in my Outlook inbox to the server?

  • 1
    Yes; What you describe is absolutely expected with the use of IMAP or Exchange. – Ramhound Jun 4 '18 at 23:45
  • Uh, did you change the existing account configuration in Outlook? I didn't know that was possible. – user1686 Jun 5 '18 at 4:34
  • No, I had to reconfigure as I migrated to a new computer. Outlook did an auto-discovery of settings and set itself to IMAP – MrD Jun 5 '18 at 9:52

When switching from POP3 to IMAP, did you import the PST file (default data file for your POP account) to your IMAP account or just attach the PST file as an additional PST file? Attached PST file won't sync back to mail server, while imported PST file will sync all imported data to mail server.

| improve this answer | |
  • Re-imported the PST, I see now what happened... – MrD Jun 5 '18 at 9:51
  • IMAP syncs emails between the server and Outlook. Once emails imported from PST, the changes will sync back to your mail server. You may try using Archive feature to export unwanted emails from your mailbox to local PST file. – Steve Fan Jun 6 '18 at 1:42

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