I committed a cardinal sin... I posted a problem I had on a forum, and then once I found the solution I didn't come back to post it! My apologies. Anyway, in my last comment I said I was going to implement DKIM and DMARC for my domain since it's a good thing to have anyways. I can confirm that once I did that my mail issues with sending to comcast.net users was resolved. No more missing emails getting dropped entirely instead of bounced (which should NOT be happening Comcast... if it's rejected for any reason it deserves to be bounced so mail admins like us have some idea what's going on), and no more being delivered straight into the spam folder on the rare occasion the email did go through. I've now sent probably 40+ emails to comcast addresses since and haven't had a single issue. @WBLIBAdmin - I think this is your answer (assuming you were in fact having the same issue I was) The lesson here is for whatever reason, even though it's not required by Gmail, Yahoo, Outlook.com, etc, if you want your email to make it to comcast.net Inboxes; your domain's, IP's, and individual email's good or perfect spam scores are completely irrelevant. In addition to SPF you MUST also have DKIM (and possibly DMARC) established for your domain. This is obviously not the global standard for handling email, but it is the comcast standard apparently. @ComcastCSAEmail - Please spread the word. If you happen to see similar posts in the future, let them know Comcast requires SPF, DKIM, (and DMARC?), for mail to even have a chance of being accepted. It would be even better if this somehow got added to a FAQ for hosts or providers. i.e. "My emails don't seem to reach comcast.net users but everyone else is getting them just fine and my spam scores are perfect, what's going on?".
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