Send Failures in Marketo

[taumueller]

Hi there- 

I have been digging around for a document that may be helpful and provide additional detailed information on Marketo email failure reasons. Below are some of the failures we are receiving and have questions on.

550 5.1.1 User unknown - this email is correct....is the company blocking it?

550 5.7.1 Relaying denied - this email is correct..... is the company blocking it?

550 [internal] [oob] The recipient is invalid - correct email on our end

550 [internal] [oob] The recipient is invalid - updated email and it still won't send

Marketo Entry ID# 1319735: 550 Invalid Recipient 550 permanent failure for one or more recipients - updated email, still not sending

5.4.1 Recipient address rejected: Access denied - first communication delivered, others weren't.

553 sorry, no mailbox here by that name - correct email address.

[Darshil_Shah1 · Accepted solution]

Below is a brief about each of the bounce codes you listed in your question. I hope this is helpful to you. Not all errors are caused because the email address is invalid, some are also caused due to the sender not being authorized, blocked, etc. too.

1. 550 5.1. 1 means that the recipient email server considers that the email address doesn't exist at the destination domain, and therefore has no way to deliver it. Unless you made an error typing out in the email address, this is not something for you to correct and needs to be corrected on the receiving end.
2. 550 5.7.1 Relaying denied: The error 550 5.7.1 generally implies that the sender is not authorized, and therefore, fails to send emails. As a result, the message is relayed back to the server.
3. 550 [internal] [oob] The recipient is invalid: This indicates that the bounce message was "Out Of Band" (sometimes mistakenly called “Out Of Bounds), meaning that the recipient mail server first said that it would accept the email, but then afterward (in a second “band” of communication) said it had been rejected. More info about this is here.
4. 550 permanent failure for one or more recipients: If you send spam emails frequently (or your emails are marked as spam frequently by recipients), there are chances of the recipient’s mail server blacklisting the mail coming from you. So, if you get a “550 permanent failure for one or more recipients” error, the first thing you have to do is to confirm whether your server IP has been blacklisted or not.
5. 5.4.1 Recipient address rejected: Access denied: Where you see the information stating that the address has been rejected, this has been generated from the receiving server, so for whatever reason, the organization that is receiving your email, has rejected your email… this may be intentionally, accidentally or temporarily out of your control.
6. 553 sorry, no mailbox here by that name: This error happens when the recipient's address is invalid. Are you sure that the email address isn't invalid?

Please let us know if you have questions. 🙂

[SanfordWhiteman]

In addition to Darshil’s specific points, more generally you must realize that a receiving mailserver is under no obligation to tell you the actual reason they’re rejecting your email. Moreover, if they want to send a permanent rejection because they consider you a spammer, it’s in their best interest to act as if an email address doesn’t exist, because for your purposes it does not.