Client has a new mac and is setting up his email we tried connecting as IMAP and the Exchange options and each time the response on screen was, "Unable to Verify Account Name or Password".   We verified the creds in webmail without any issue.  I can see in the user connections on the mail server connections coming in to the server. 
No joy what-so-ever tried IMAP ports 143 and 993 every entry was the same response.