Bounces from valid email addresses. How do you handle?

We see this one quite often: 550 [internal] [oob] The recipient is invalid.  I often chalked it up to mean the email server initially accepted delivery – probably into some sort of spam catcher (marking the email as “delivered”); and then bounced back the specific code (“550 [internal] [oob] The recipient is invalid”), letting Marketo know that this is an invalid email address.

We're finding more and more false positives in our email sends - especially from a delivered, open and click perspective, where one or all of this activity includes some sort of bounce notification at about the same time the positive activity takes place.

Our bounce policy is much less forgiving than this - especially on the hard bounce side.

Dory, I would want my team to look into your concern a little more deeply.  I am surprised to see that Marketo is capturing what look like invalid address bounces

• 550 [internal] [oob] The recipient is invalid.
• 550 5.1.1 User unknown

for addresses you are actively communicating with.

The behavior you describe of mail bouncing and also showing activity is also unexpected behavior:

We would only track a bounce if the recipient's mail server returned a bounce.   In this case Marketo's mail servers received a message indicating the mail was delivered and another that it bounced.  I would need to look at the specific delivered & bounce responses to understand why we are seeing both activities. 

Speaking specifically to the 550 [internal] [oob] The recipient is invalid bounce. Any time there is a [oob] this means the email bounce was returned through an Out Of Band process.  In this case the receiving email servers accept all messages and return a delivered response to our servers.  THEN they process the mail.  In the case of invalid addresses or spam filtering the receiving email network will return a bounce response after processing.  In these cases we will receive both a delivered and a bounce in the case of undelivered email. 

An Exchange (incl. Office 365) server rejecting you based on the envelope sender (*@*.mktomail.com).

Anastasia, That is bounce is not specific enough to identify the exact cause, this could be IP or domain based.  There is an escalation path with Microsoft to troubleshoot that bounce.   Please create a Support case so they can troubleshoot to my team for review and escalation to Microsoft if necessary.

Thank you,

Kiersti

Kiersti Esparza

Manager, Privacy & Deliverability Team, Marketo, Inc.