If you're not receiving any messages that have been sent to you, there's a few potential reasons and fixes:
1: Ensure that messages are actually being sent - get someone else to send you an email from an external address. The original sender may be experiencing issues, rather than the receiever.
2: Log in to ESA as an administrator.
3: Click the account not receiving mail in the User List.
4: Disable any Delete Thresholds (these can be set to delete any overly spam-like messages, but settings may be overly restrictive).
5: Check spam filter locations like spam@domain-name mailbox (may be a different address) and the user's spam folder - messages may have been filtered wrongly.
6: See if the sender has received an error or bounce message - this message can be explained by the correspondant's ISP, or can be sent over to us to diagnose.
If none of these suggestions work, get in touch with the Exa Support team. You can reach us by:
Phone: 0345 145 1234
Fax: 01274 911 855
Email: (not recommended if you're having issues with receiving mail): firstname.lastname@example.org