Sendmail/Blacklists rejecting authenticated users

Quick question regarding dnsbl's...  The other day I was in the 
Pittsburgh airport trying to send an email using their free wifi.  
Unsurprisingly this network's ip range is listed on a few of the 
blacklists. This resulted in my mail server rejecting my connection when 
I tried to send some emails.  Does anyone know how I can configure 
sendmail/procmail to not check the IP addresses against the dnsbls for 
authenticated users?  I have already done a fair amount of googling but 
haven't come up with anything workable, nor can I think of a good way to 
test (since I don't have access to a blacklisted network). 

Thanks,
Mike