invalid domain counted as "soft bounce"

[MaximilianKohler]

Version:

• listmonk: [v2.5.1]
• OS: [ubuntu]

I guess it's because Amazon SES is labeling it as "bounceType": "Transient", and that's what listmonk is reading? If so, perhaps the solution is to read the "status code" instead?

  "bounce": {
    "timestamp": "2023-08-17T14:40:18.000Z",
    "bounceType": "Transient",
    "feedbackId": "01110184444444444444436605-000000",
    "reportingMTA": "dns; amazonses.com",
    "bounceSubType": "General",
    "bouncedRecipients": [
      {
        "action": "failed",
        "status": "5.4.4",
        "emailAddress": "[email protected]",
        "diagnosticCode": "smtp; 550 5.4.4 Invalid domain"
      }
    ]
  },
  "notificationType": "Bounce"
}

EDIT:

Relevant links I could find:

• https://repost.aws/knowledge-center/ses-understand-soft-bounces
• https://docs.aws.amazon.com/ses/latest/dg/receiving-email-action-bounce.html

In my opinion, this is more of an error on Amazon's end (misclassifying), so I'll find a way to contact them as well.

[MaximilianKohler]

Here are some examples, but I haven't found a complete list yet:

    "bounceType": "Transient",
        "bounceSubType": "General",
        "status": "5.4.4",
        "diagnosticCode": "smtp; 550 5.4.4 Invalid domain"

    "bounceType": "Permanent",
    "bounceSubType": "General",
        "status": "4.4.2",
        "diagnosticCode": "smtp; The email account that you tried to reach does not exist."
      }

    "bounceType": "Permanent",
    "bounceSubType": "General",
        "status": "5.1.1",
        "diagnosticCode": "smtp; 550 5.1.1 user unknown"
      }

    "bounceType": "Permanent",
    "bounceSubType": "General",
        "status": "5.1.1",
        "diagnosticCode": "smtp; 550-5.1.1 The email account that you tried to reach does not exist."
      }

    "bounceType": "Permanent",
    "bounceSubType": "General",
        "status": "5.5.0",
        "diagnosticCode": "smtp; 550 5.5.0 Requested action not taken: mailbox unavailable"
      }

    "bounceType": "Transient",
    "bounceSubType": "MailboxFull",
        "status": "4.4.7",
        "diagnosticCode": "smtp; 554 4.4.7 Message expired: unable to deliver in 840 minutes.<452-4.2.2 The email account that you tried to reach is over quota."
      }

[MaximilianKohler]

Thank you for fixing this @knadh! I think I found another one:

  "bounce": {
    "bounceType": "Transient",
    "bounceSubType": "General",
    "bouncedRecipients": [
      {
        "action": "failed",
        "status": "4.4.7",
        "emailAddress": "[email protected]",
        "diagnosticCode": "smtp; 550 4.4.7 Message expired: unable to deliver in 840 minutes.<421 4.4.1 Failed to establish connection>"
      }
    ]
  },
  "notificationType": "Bounce"
}

  "bounce": {
    "bounceType": "Transient",
    "bounceSubType": "General",
    "bouncedRecipients": [
      {
        "action": "failed",
        "status": "4.4.7",
        "emailAddress": "[email protected]",
        "diagnosticCode": "smtp; 550 4.4.7 Message expired: unable to deliver in 840 minutes.<421 4.4.0 Unable to lookup DNS for icloud.co>"
      }
    ]
  },
  "notificationType": "Bounce"
}

But this one's tricky since the full "diagnosticCode" varies, and they also use "4.4.7" for legitimate transient bounces:

  "bounce": {
    "bounceType": "Transient",
    "bounceSubType": "MailboxFull",
    "bouncedRecipients": [
      {
        "action": "failed",
        "status": "4.4.7",
        "emailAddress": "[email protected]",
        "diagnosticCode": "smtp; 554 4.4.7 Message expired: unable to deliver in 840 minutes.<452-4.2.2 The email account that you tried to reach is over quota. Please direct<CRLF>452-4.2.2 the recipient to<CRLF>452 4.2.2  https://support.google.com/mail/?p=OverQuotaTemp o15-20020a170902d4cf00b001bbe7fae392si3002811plg.335 - gsmtp>"
      }
    ]
  },
  "notificationType": "Bounce"
}

Though it seems consistent that they use "mailboxfull" subtype for legitimate ones, and "general" for unreachable domains:

  "bounce": {
    "bounceType": "Transient",
    "bounceSubType": "General",
    "bouncedRecipients": [
      {
        "action": "failed",
        "status": "4.4.7",
        "emailAddress": "[email protected]",
        "diagnosticCode": "smtp; 550 4.4.7 Message expired: unable to deliver in 840 minutes.<421 4.4.0 Unable to lookup DNS for budness.net>"
      }
    ]
  },
  "notificationType": "Bounce"
}

EDIT:

  "bounce": {
    "bounceType": "Transient",
    "bounceSubType": "General",
    "bouncedRecipients": [
      {
        "action": "failed",
        "status": "5.4.14",
        "emailAddress": "[email protected]",
        "diagnosticCode": "smtp;554 5.4.14 Hop count exceeded - possible mail loop ATTR34 [HK2PEPF00006FAE.apcprd02.prod.outlook.com 2023-08-21T14:43:08.787Z 08DB9D59A1939BE8]"
      }
    ]
  },
  "notificationType": "Bounce"
}

This bounced immediately (not after some days as with the "mailbox full" transient bounces), and the email notification I got was:

Your message to [email protected] couldn't be delivered.
eg wasn't found at proton.com.

So this is another hard bounce that is being recognized as a hard bounce by everyone except Amazon SES. I sent general feedback to Amazon about this but I'm doubtful they'd do anything.

I kind of just want to count all the transient subtypes with "bounceSubType": "General", as a hard bounce. But I found one with no description, and I haven't gotten an email notification for it either:

  "bounce": {
    "bounceType": "Transient",
    "bounceSubType": "General",
    "bouncedRecipients": [
      {
        "emailAddress": "name <[email protected]>"
      }
    ]
  },
  "notificationType": "Bounce"
}

Maybe it was an "automatic response" mentioned here https://docs.aws.amazon.com/ses/latest/dg/notification-contents.html#bounce-types