This is the error I get in the messages window:
Failed to connect to mail server smtp.office365.com; error message: NTLM authentication: Timeout.; SASL DIGEST-MD5 authentication: Timeout.; CRAM-MD5 authentication: Timeout.; APOP authentication: Timeout.; SASL Plain authentication: Timeout.
Any ideas as to what might be incorrect in my settings?
Solved.
The server name and port number were incorrect. Once I changed them everything started working as it should...
