Comcast is Blacklisting this Site's Email Server

Comcast is blacklisting our mail server and has done so for the past several months or possibly more. It probably isn't targetted at this site, so much as it is targetted at part or all of Jaguarpc.com (where we are hosted). So it could be any one of thousands of sites hosted on Jaguarpc that sent out spam or email that was perceived to be spam.

This means that people with Comcast email addresses:
1) do not get confirmation emails
2) cannot reset their passwords
3) do not get email newsletters

In general, Comcast users won't get ANY email from this site.

I've been trying to fix this solution for a couple months, but haven't made any progress. Recently I got a phone number for Comcast, so I'm going to try and get the JaguarPC support team to make a call to solve the problem.

The site has a dozen or more users on Comcast (including one who wants to implement the software for a union), so this is annoying.