EMail Timeout Issue and lost attachments

Hi,  I recently updated the NIS and now have an eMail issue.  eMail is slow.  There may be multiple issues here but I just noticed that there is frequently  the following type of text pre-pended to many of the eMail now received at my desktop:

X-Symantec-TimeoutProtection: 0
X-Symantec-TimeoutProtection: 1
X-Symantec-TimeoutProtection: 2
X-Symantec-TimeoutProtection: 3
X-Symantec-TimeoutProtection: 4
X-Symantec-TimeoutProtection: 5
X-Symantec-TimeoutProtection: 6
X-Symantec-TimeoutProtection: 7
X-Symantec-TimeoutProtection: 8
X-Symantec-TimeoutProtection: 9
X-Symantec-TimeoutProtection: 10
X-Symantec-TimeoutProtection: 11
X-Symantec-TimeoutProtection: 12
X-Symantec-TimeoutProtection: 13
X-Symantec-TimeoutProtection: 14
 

What does this mean?  What are the ramifications?  Is there a log file somewhere that may better explain these frequent incidents? eMail senders have reported sending attachements that I do not receive.  This is my best clue so far....  but I dont know if its the culprit.

Thanks for any assistance or ideas.

Jeff 32767