The content of the email was really not a concern, I could reproduce will emails containing a simple 'test' text in it.
After further testing and trying from a different endpoint/platform, it turns out I am not getting the same behaviour from all clients/MUA. Re-enabling 'reject_unknown_recipient_domain', if I send another test email from my webmail, I get a notification from the webmail that the email was not sent due to a bad address. The email is not sent to anyone and I have to edit/fix my list of recipients before being able to send the email. If I test from K9-Mail on Android, I get the same error as yesterday, the sending of the email is considered failed but stays in the Outbox, where it keeps trying to send the email periodically, but with a header that is now actually broken, missing several fields. >From one of the recipients'mail server I received a notification mentioning: Missing required header field: "Date" Missing required header field: "From" MIME error: error: unexpected end of header So, my guess is that the issue resides with K9-Mail way of handling the reject server response, as it somehow mangles its own header. Does that make sense? -- Sent from: http://postfix.1071664.n5.nabble.com/Postfix-Users-f2.html
