So I dont know if Office365 (aka online Office w/ Exchange) is like standalone server version of Exchange, but in order to let the webserver communicate with our Exchange server initially we had to create a rule that allowed it.If I remember correctly it was at: Exchange Management
Console ->
Server Configuration -> Hub Transport -> Receive Connectors. I imagine that its similar in the online version.Also users had to be granted permission to to use POP/IMAP in Exchange (note I don't recall how to do this, but I seem to recall it being enabled in their user profile in Exchange). Another note I recall that POP/IMAP was not enabled at the Exchange side either and had to be.I have never used Exchange Online (Office365) so this post is speculation.