Is there any way to make this Discourse feature work with Mailgun?
It should be possible to show at least the error code and message:
Both SMTP error code and SMTP error message are preserved
“code”: 550,
“address”: “'baz@example.com”,
“error”: “Message was not accepted – invalid mailbox. Local mailbox 'baz@example.com is unavailable: user not found”
https://documentation.mailgun.com/en/latest/api-bounces.html#examples
If not then at least we need a sensible error message to explain why the link doesn’t work 