I had a client report that an email sent out to all staff was not delivered to some staff members.  When I searched the archive the message did not show up.  I traced back to the SMTP logs at the moment when the  message was delivered to the mail server.  I matched up the To emails in the logs to the To emails in the original email.  The 1st 20 recipents were processed correctly.  But on the 21st, the sender had a recipient that was no longer with the company, and their account had been deleted.  The mail server said "No such user here" and then disconnected, and did  not process the remaining recipients.  I think there could be a bug with how SmarterMail deals with these situations.  I am currently running Build 6996 of SmarterMail.  I will update to the latest release, but in case this is a new bug I wanted to bring it to everyone's attention.