Web services and firewalls

To my understanding a web service uses port 80. We have a number of clients
that are having a problem connecting due to their firewalls. Is there
something I can do to correct the problems? Is it possible that the response
from the web service is coming in on a different port?

Thanks,
JoeMost web services default to port 80. SSL is 143? Something odd if
it's secured. However, if the problem is connecting i'm assuming they
can't get any other internet either without having the same problems.
I would check to see what port your IIS(ISM) is serving the web browser
on. Also check to make sure it's on their trusted list for their
firewalls or not blacklisted if they use a blacklist.