This may be a known error but I found out thru the blogoshere that it looks like a Comcast problem. Is there a way to circumvent this issue? All my "comcast.net" emails are bouncing.
Here's what I found out:
I figured it out. I thought I would document it here in case anyone else needs help in the future.
The sender of the email was coming across at comcast as ‘firstname.lastname@example.org’, which comcast was trying to verify.
I needed an additional MX record. I use Google Apps for normal emails, but also Mailgun. I had all the Google Apps MX records, but what I had to do was add an additional MX record with a subdomain of “mg” for mailgun, which I just pointed at google server. Here are my MX records, which seem to now be working:
MX Records Mail Server Preference Subdomain TTL aspmx.l.google.com 1 Default alt1.aspmx.l.google.com 5 Default alt2.aspmx.l.google.com 5 Default alt3.aspmx.l.google.com 10 Default alt4.aspmx.l.google.com 10 Default aspmx.l.google.com 20 mg Default