Microsoft Exchange - mailmate/mailmate_manual GitHub Wiki

MailMate supports IMAP and IMAP only for incoming email and this is a severe problem for some users of MailMate. There are 2 variants of this problem:

• Users forced to use an Exchange server which does not have IMAP support enabled.
• Users forced to use an Exchange server with IMAP enabled (including Office365 accounts), but two-factor authentication is mandatory and the OAuth2 authentication method is not available to third party applications like MailMate. (Note that outlook.com is a notable exception for which MailMate does work with IMAP and OAuth2.)

Update February 2021: During 2020, Microsoft added OAuth2 support for IMAP/SMTP clients for Office365 accounts. Currently, only test releases of MailMate will allow users to use this to connect Office365 accounts. Note that you might still need to be allowed to use MailMate by your IT department/organization.

In any case, the above requires the user to find a different solution. The following are the currently known options.

Switch to an email client which supports the native Exchange protocol. To my knowledge, the only options on macOS are currently Outlook, Apple Mail, and AirMail.

Pros: It's simple.

Cons: You don't get to use MailMate any longer.

Redirect all emails to a separate email account which does support IMAP. Preferably an account which does not receive any other emails. Then setup this account in MailMate with the email address used on the Exchange server and configure the Exchange SMTP server for sending. The latter is important for “hiding” that the redirection happens. Look for redirection instructions on this page. Do not use forwarding.

Alternatively, an email client which supports native Exchange (see 1.) could be used to fetch and move the emails.

Pros:

• As long as the redirection works, the IMAP server can be as good/robust as you like. No problems with Exchange bugs.
• It also works with other IMAP email clients.

Cons:

• Redirection to a different server might be against company policy.
• Tags in MailMate cannot be synchronized with the server (they have to be local only).
• Changes cannot be synchronized back to the Exchange server.

Install a DavMail gateway. This provides an IMAP interface on your machine which MailMate can use. The gateway then takes care of talking to the Exchange server. According to the release notes, the gateway also supports OAuth2 authentication.

Pros:

• The emails do not have to be redirected to a different email account.
• Changes can be synchronized back to the Exchange server (moving, deleting, flagging, unread state).
• DavMail can be configured to map MailMate tags to Outlook categories.

Cons:

• It's probably not easy to setup for the average user.
• It's another point of failure and Exchange IMAP is already very buggy by itself.
• It only works when the machine running DavMail is running.