Anyone has same mail issue?

some of my customers has this issue intermitentelly:

Receving from outlook express or Netscape , in some point of the download (for example 5/10 messages) is waiting until get timeout and an error.

The next time start in message 1 , 2,3,4,5 …and in the same point it is waiting server response… and so forever. The customer is receiving message 1,2,3,4 one time and another time, and other time…forever… and never receive the messages number 5,6,7,8,9,10

The only workaround I found was login in webmail and delete message number 5. After that all is running fine..

I don’t find any solution for that, and it is occurring is several customers with differents domains, differents networks, etc..
This is at least 1 time a month

The error outlook or netscape get is wrong because the description is some like: “…this is part of the text message…”
This is not an error, it is part of the text message

This is like Mail Server had lost the pointer (C programmers will know what I’m saying) and it was reading (or previously writted) in a wrong position.

Somebody has experimented this issue?