Settings at a Glance

IMAP was designed to only sync mail messages between your computer and your mailserver. For connecting to the Exchange mail service, IMAP is not recommended for these reasons:

• IMAP does not support calendar integration. Selecting “Exchange” rather than “IMAP” in Outlook (PC/Mac), Mail.app (Mac), or the built-in mail apps on your iOS, Android, Windows or Blackberry smartphone, synchronizes not only your email, but also your calendar and address book.
• The most common IMAP email clients are either no longer supported (e.g. Eudora), or have minimal support (e.g. Thunderbird).
• Thunderbird has difficulty filing “sent” messages in the “Sent Items” folder on Exchange mail servers. Sent messages by default end up being saved on the local drive of the computer running Thunderbird. There is a work around, but many Thunderbird users are unaware there even is problem until they lose the only copy of their “sent” messages when their computer fails or is lost.
• Duo users cannot use IMAP as Microsoft does not support 2-factor authentication over IMAP.

The above reasons not withstanding, one might still choose to use an IMAP client of their choosing, but at least keep a bookmark to the Exchange O365 webmail site handy, as a fall-back: exchange.carleton.ca