Once in a while I get emails with no subject and the senders field is also blank.
If I use ms outlook, I can get access to all my emails.
For those of my users using outlook express, I've noticed that they can download mail until it reaches the message with the blank address and sender field.
Once it reaches that message, it stops and does not download anything futher.
It happens to all my outlook express users who have to pull down messages with blank addresses and subjects.