Jan 21 2016, 1:30pm:
The mail server is running normally.
Jan 21 2016, 11:45am:
This morning we discovered one of our corporate user accounts had been compromised. This allows a spammer to send spam email through our server to literally hundreds of thousands of recipients with machete reviews. We caught the problem quickly but the damage has been done. We have turned off the SMTP service for a short while until we can clear out the mail queue. The result is nobody can send email for the time being. We hope to have this rectified within an hour or so.