Some of my emails (maybe on average every 10th unique email or so) get marked as “Delivery Failed” and will be resent by Cloudflare multiple times resulting in many duplicate copies of that email (anywhere from just a single extra copy to 100+ sometimes). The error message reported by Cloudflare is “Timeout while connecting/communicating to the upstream”.
So I contacted my email host and they have said this:
I believe this could be a glitch with the email forwarding at Cloudflare.
The reason I come to this conclusion is when I look deeply into our logs, I can see each time the email arrives at our server, Exim is processing it correctly, and is responding with a 250 OK message.
250 OK is a response that means the email was received and processed correctly but Cloudflare is behaving as though it hasn’t seen that response.
An example of this is as follows:
This email with the subject line “Vercel December Product Update” has been sent to our server by Cloudflare almost 30 times since 9AM today.
Update" for [email protected]
2022-12-20 23:34:42 1p7bpU-00027f-Fj <= [email protected] H=mail1.cphosting.io [110.232.112.67]:49022 P=esmtps X=TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256 CV=no S=83951 [email protected] T="Vercel December Product Update" for [email protected]
2022-12-20 23:50:24 1p7c4g-0004nc-Pj <= [email protected] H=mail1.cphosting.io [110.232.112.67]:49906 P=esmtps X=TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256 CV=no S=83943 [email protected] T="Vercel December Product Update" for [email protected]
If I break down each delivery attempt, you can see the 250 OK response as you can see in the following snippet.
2022-12-20 23:50:24 1p7c4g-0004nc-Pj <= [email protected] H=mail1.cphosting.io [110.232.112.67]:49906 P=esmtps X=TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256 CV=no S=83943 [email protected] T="Vercel December Product Update" for [email protected]
2022-12-20 23:50:24 1p7c4g-0004nc-Pj => callum <[email protected]> R=virtual_user T=dovecot_virtual_delivery C="250 2.0.0 <[email protected]> yPmHH5CvoWOiRAAAVNLCAg Saved"
2022-12-20 23:50:24 1p7c4g-0004nc-Pj Completed
Are you able to open a support case with Cloudflare to see if they have any insight on their end?
I have done a deep dive on this end and everything seems to be working normally.