When Norton Anti-Virus (and SpamPal) processes a large message,
it has to process all the mail body (not just the headers).
Where SpamPal send one byte at a time of header, to the email
program (as a keep alive signal), Norton sees this and tries
to generate an extra header line: X-Symantec-TimeoutProtection:0
It generates a number of these in sequence, changing the number
at the end, as a way of keeping the flow of data going when
scanning a large attachment.
So, if you have one such header, it means that the time interval
between its keep alive packets, is still greater than the
timeout setting
for your email program, so you could try to increase this
timeout.
You can also try and help Norton out, by just using just one
DNSBL, e.g. SpamCop, and set the timeout
on DNSBL queries to something
low, e.g. 10 seconds.
Note
2: Upgrading from NAV 2000
Although
there is no special set up required for Norton 2002, it appears
that quite a few people upgrade from Norton 2000, and don't
properly uninstall the Norton 2000 POP3 proxy, and get the
port unavailable error
message without knowing why.
Advice
for this situation is to make sure you have properly
uninstalled the previous version of Norton.
