Configuring Monit to Send Mail through Office365

"504 5.7.4 Unrecognized authentication type" is a response to your request. It means you are requesting access via an authentication type that is not supported by the connection.

I am not familiar with MONIT - so I can't help with the configuration completely but review these configuration items:

1. Be sure that the FROM in the message is the same as the account you are logging in as.
2. Check the Authentication type directly that is also being passed. If your configuration shows AUTH LOGIN Try to change that to AUTH BASIC.
3. O365 supports TLS 1.0, 1.1, and 1.2 - however, you must also be sure you have the proper cipher suites enabled that are supported by O365 or a connection will not be made. See here for supported cipher suites: https://technet.microsoft.com/en-us/library/mt163898.aspx To find what you are using or trying to use - you need to do a packet trace - which will show you which protocol you are using, version, and the cipher suite (or if you are not using a compatible one). Use something like WireShark to get this info. All OSes will have a default set of cipher suites enabled - but will let you enable others as well as change the order they are attempted.