554 5.4.5 internal Delivery not attempted message expired

[Anonymous]

I deployed an email campaign last week and received the below soft bounce error message for about 60 leads this campaign was deployed to:

554 5.4.5 [internal] Delivery not attempted (message expired)

These 60 leads are comprised of clients at two different firms. We have successfully been able to email them in the past, so I am not sure why they bounced for this specific email. Can someone decypher what this error message is saying and why these leads bounced?

I found this article that looks like it might be Network Congestion:
https://community.marketo.com/MarketoDiscussionDetail?id=90650000000Ph6TAAS

Does this just mean at the day/time I sent these campaigns, these firms were experiencing "congestion" for that 36 hour period? If so, is there any best practices on how to avoid this and should I attempt to resend them this campaign?

[Anonymous · Accepted solution]

Hi Bethany, that's correct, this error code is in regards to the recipient's email server basically having too much traffic to accept your mail.

I would just suggest not emailing thousands of contacts at the same company all at once (not that you did that last time around) and just try mailing to those particular leads again in a day or so.  I'm not sure there is much else you can do as, again, this really has to do with the recipient's server, but maybe play around with sending at different days during the week or during off-peak email traffic times - might help more mail get through.

[SanfordWhiteman]

@Bethany D "Congestion" is usually a euphemism.  Doesn't mean the server is actually too overwhelmed to handle your email.   It means they've handled enough email from you already in the past hour/day/other period.  The technically more appropriate response code is actually 4.4.5 (not 5.4.5) which would mean "temporary congestion." But 4xx codes signify transient states, meaning mail would be retried continually -- not what the server wants in this instance.  Thus 5.4.5 is used instead: 5xx codes are permanent failures that require users to resend manually.

Like @Nate A says you need to space out your sends if this happens.

[Anonymous]

I have a question about this particular error too - if we're getting this message because the volume is high and Marketo keeps trying them, won't we continue to get this message because of the volume? (it's like a circle!)  How else can I stagger the delivery to ensure we aren't hitting a server with 400 messages all at the same time and then repeating that 400 messages over and over.  I'm using a basic email campaign to a smart list of users and I would hate to have to separate groups out by domain.