Fetchmail/Sendmail problem

[Mike keithley]

This is probably off topic but the problem occurs getting mail from this
list so I thought I'd ask the experts.

I use fetchmail to get mail from shellworld.net (my ISP).  Fetchmail
negotiates with sendmail to get mail into my local mailbox.  Sendmail seems to 
want to verify that the sender domain is valid and checks a route.  
the intermittent problem is this:

braille.uwo.ca doesn't always have a route and the system waits forever
until shellworld's pop server times out.  On my mailbox at shellworld, 
the retrieved message, that wasn't delivered, is marked as read.  

This problem is intermittent and was very bad around the middle of
May.  It went away and is now back.  I tried "nslookup braille.uwo.ca" 
and, sure enough, I got "non-existent domain name".

So the questions: is there a way I can tell sendmail not to verify a
sender's domain?  Do I have a network problem?  Why is the problem 
intermittent?

I'm attaching part of the fetchmail log pertaining to a message that
behaved this way:

fetchmail: POP3> RETR 3
fetchmail: POP3< +OK 3406 octets
reading message 3 of 5 (3406 octets)
About to rewrite Return-Path: <speakup-admin at braille.uwo.ca>
Rewritten version is Return-Path: <speakup-admin at braille.uwo.ca>

About to rewrite From: "Raul A. Gallegos" <raul at asmodean.net>
Rewritten version is From: "Raul A. Gallegos" <raul at asmodean.net>

About to rewrite To: "speakup at braille.uwo.ca" <speakup at braille.uwo.ca>
Rewritten version is To: "speakup at braille.uwo.ca" <speakup at braille.uwo.ca>

About to rewrite Sender: speakup-admin at braille.uwo.ca
Rewritten version is Sender: speakup-admin at braille.uwo.ca

About to rewrite Reply-To: speakup at braille.uwo.ca
Rewritten version is Reply-To: speakup at braille.uwo.ca

fetchmail: forwarding to localhost
fetchmail: SMTP> MAIL FROM:<speakup-admin at braille.uwo.ca> BODY=7BIT SIZE=3406
*** wait about 60 seconds ***
fetchmail: SMTP< 451 4.1.8 <speakup-admin at braille.uwo.ca>... Sender domain must resolve
fetchmail: SMTP> RSET
fetchmail: SMTP< 250 2.0.0 Reset state
fetchmail: Saved error is still 451
 not flushed
fetchmail: POP3> RETR 7
fetchmail: POP3< -ERR POP timeout
fetchmail: POP3> QUIT
fetchmail: POP3< +OK Pop server at ns signing off.
. 
. 

Thanks