#5.5.0 smtp;554 Transaction Failed Spam Message not queued

[3rik7]

We're suddenly having an issue sending to one particular domain from our Exchange 2003 server. I've spoken to an IT person on the recipient side and they say it's not their problem (its a government agency). Here are the details -

Specific NDR message - <mail.ourdomain.com #5.5.0 smtp;554 Transaction Failed Spam Message not queued.>

Checked MXToolbox and we're not blacklisted.

Using Exchange Message Tracking, the last 3 lines for the bounced message are - SMTP: Message Routed and Queued for Remote Delivery, SMTP: Started Outbound Transfer of Message, SMTP: Non-Delivered Report(NDR) Generated.

And one last, slightly baffling fact, it seems to be only happening when replying to an email sent from the other domain. If we start a new email sent to the other domain, it goes through fine. The other domain replies to us, we reply back and then it fails.

I'm not sure where else to look or what else to check.
Anybody have any ideas or advice?

Thanks,
Erik

 

[Zelandakh]

I saw this a couple of weeks ago with a customer but can't recall the solution

Try deleting and recreating the smtp connector.