Qmail issues w/ Verizon & Earthlink
I run a qmail + spamassassin + clamav Slackware 10.1 email server for a local ISP. Recently some users have complained that people on earthlink/verizon cannot email them. I have checked my qmail logs and I see my server emailing verizon/earthlink but I see no ips from them emailing my sever (unless they use a ip for their smtp servers I was not aware of). Since their simple lusers who just want to send/recieve email they cannot tell me if the earthlink/verizon person is getting a email back saying why it was rejected. And of course verizon/earthlink say its on my end.
Any ideas what I should look for on my server? Has any other email admins had these issues lately?