I have a client telling me that they get this error when sending us emails with attachments only. They can send regular email no problem. But when they throw an attachment on it they get
#< #4.4.7 smtp;550 4.4.7 QUEUE.Expired; message expired> #SMTP#
I think it is on their side, we can receive attachments from other people with no problems. There are at least two other people from different sources that can't send us attachements.