Bounce+ email address not verifying

I’m having trouble where one user’s email verification system rejects my forum’s emails.

I had originally set up my forum to send from a Mailgun account for, and then receive emails directly to the forum from After seeing this issue, I’ve made a second Mailgun account for so that I can set their MX records, which I read helped with verification. My notification email setting is now "".

I get this error when sending through either domain:

Failed: ‘[The Interactive Fiction Community Forum] Password reset’ Server response: 550 Verification failed for <> Unknown user Sender verify failed

The replies+ email address is correctly using the root domain so that I can receive them. The issue is that verification is failing for the bounce+ address.

Is the bounce+ email address set by Discourse, or by Mailgun? I assume Discourse or else it would be because that’s the Mailgun account I’m using. Which domain should it be using? I do have webhooks set up for Mailgun, so if it intercepted the bounces I think the forum would still be notified. Or else, if the bounce+ address should be set to the root domain so the forum can receive these bounces directly, does anyone have any advice for what else I could do to fix verification issues like this?

By Mailgun.

Something is likely wrong with your setup is sending emails with replies+verp-<guid> when it should be replies+verp-<guid>

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You sure?

I was following these instructions, which say to set the MX records directly to the forum.

If I set the reply address to then Mailgun will receive the replies, not the forum.

Yes, hence why we need to use the webhooks to be aware of the bounces :wink:

But web hooks don’t help with letting people reply via email.

Which is why the reply via email address is separate from the Mailgun domain. Either a pop3 mailbox or the simple mail receiver. They don’t need the same FQDN.

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So I think this was a weird quirk for one particular user because they used to host our domain. So let’s consider this solved now.

But I think I figured out the problem. My server still thinks it’s, so when it received incoming mail claiming to be from there, it failed verification (because my other domain is on the same server). I got the exact same thing just now after setting up one of my other domains elsewhere, and attempting to forward myself something.


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