Which Bounce Codes Should We Address with a Whitelisting Initiative?

[Danielle_Wong]

We have customers who seem to bounce many times, however, their email addresses look correct. We are looking to email these customers one on one to whitelist our Marketo sending IPs. However, would we do this for all bounces or just certain bounce codes? I'm trying to create a smart list of these people.

Thank you

[Diana_Watts3]

When you say that they 'look correct', what do you mean? 

I've noticed that we get a lot of OOB (Out Of Bounds) bounces, where the emails may well be valid but the mail server rejects them AFTER delivery. There's a good summary of it from Mike Reynolds at the end of this thread. As an organisation you can make a call on strategy - whether to override the bounce and re-deliver to these addresses again - it is possible that they will make it through on another send, but you need to balance that with reputation and what the comms actually are (operational vs marketing). 

[SanfordWhiteman]

Out-of-Band.

In-Band = rejected during the initial SMTP conversation.

Out-of-Band = rejected by a deeper hop after being accepted at the first network hop.

[Danielle_Wong]

Hi Diana Watts‌ and Sanford Whiteman‌,

Thanks for replying to my question.

When I said that the email address looks correct, I mean that via one-to-one communication with these bounced emails, we do get a reply, however, when we send them communications via Marketo campaigns, they bounce. 

It might be important to note: We don't have a dedicated IP, we're on a shared one. 

Some bounce codes I'm seeing are:

554 sender is rejected: 16

550 Mail could not be processed

550 Denied by policy

550 5.7.1 <em-sj-02.mktomail.com[199.15.214.202]>: Client host rejected: Connection rejected due to site policy

554 ESMTP not accepting messages

554 sender is rejected: 63

Sanford, I do understand your reasoning for not requesting to be whitelisted, but worth a try, right? 

I'm going to continue to try to build the smart list based on this /blogs/marketowhisperer/2015/08/18/monitoring-email-deliverability-troubleshooting-spam-blocks-part-.... 

Thanks!

Danielle

[SanfordWhiteman]

It might be important to note: We don't have a dedicated IP, we're on a shared one.

Yep, assumed that (since most Marketo users are) and that's why you can only safely be whitelisted using DKIM. But like I said, you may get someone to consider your request using other, more inclusive methods.

Those response codes clearly state they don't want to accept mail from Marketo, so good luck!

[SanfordWhiteman]

Like Diana, I wonder what you mean by "look correct" -- either you can send to that same address via your corporate email server or not, no?

As far as what response codes, if the recipient's domain can receive mail from your corporate side, then unless the bounce reason is explicitly "mailbox full" (as opposed to "mailbox does not exist", which is likely to be spurious) you might as well include it in this initiative.

However, I'm generally against whitelisting as usually formulated because you're asking IT people to be far too broad in turning off their own email filters. The only safe, non-side-effecting way to whitelist is based on a valid DKIM signature from your domain. (Their IT staff may not have the ability to understand/implement this level of precision, unfortunately.)