Deliverability of Distribution List to Gmail - UnsolicitedRateLimitError Error

Copper Contributor

Hi!  I have an exchange server set up with several distribution lists that include users with gmail accounts.  Sometimes gmail rejects the emails with this error:


Remote server returned '550 5.4.300 Message expired -> 421 4.7.28 Gmail has detected an unusual rate of unsolicited mail. To protect;our users from spam, mail has been temporarily rate limited. For;more information, go to; to;review our Bulk Email Senders Guidelines. j11-20020a05620a146b00b0078734c20d5asi153486qkl.360 - gsmtp'


I have reviewed the suggested information and done my best to ensure that everything in my DNS and exchange configuration is correct. 


I've also reviewed the domains spam reputation and it is clean.


We are not bulk senders (unless our e-newsletter hosted elsewhere counts toward this).  The exchange distribution lists only have about 10 emails on each.


I can post one of the failed message headers if that is helpful.  The domain is


Any ideas on what else to check?  Thank you very much in advance.

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