SymptomsA customer cannot connect to their Exchange 2013 mailbox via POP3, IMAP, or SMTP if the user's UPN (User Principal Name) login does not match the mailbox's primary email address.
For example, say a customer created a user with the UPN email@example.com, created an Exchange 2013 mailbox for the user, and set the primary email address for this mailbox to firstname.lastname@example.org:
In this case, the user will not not be able to connect to their mailbox via POP3/IMAP/SMTP protocols using the email@example.com username.
The problem occurs on Exchange 2013 installations managed by POA 5.4.x only.
CauseThere is a problem in MS Exchange 2013.
ResolutionUse the user's NTLM login (DOMAIN\SAM_ACCOUNT_NAME) if the UPN login and mailbox primary email address are different. The NTLM login is shown in the POA Customer Control Panel, on the General tab of the Exchange mailbox's properties:
So, in the example above, a customer may log in to their Exchange 2013 mailbox using the HOSTING\jdoe207 username.