[NCLUG] comcast blocking port 25?

[Matt]

Hi,

A friend of mine said that Comcast blocked port 25, at least on his
machine. I don't know if comcast is selectively picking machines to
block (my friend has a mail alias that broadcasts to about 100 people
and I don't know if that is something comcast sees). If they do that
to me I want to know what I need to do. I send my outgoing email
through comcast's authenticated server (mainly so my spam filter
doesn't toss my own mail) and I assume that's OK and won't change. Is
that a bad assumption? I receive my email on port 25, too. Will that
be blocked? My understanding is that port 587 should be used. Should I
configure postfix to look at both 25 and 587?  If so, how?

Thanks,

Matt