Issues with NDR Delay going to specific domains

[brockj]

I have been googling this and most things seem to point to DNS issues, and that looks clean from what I am seeing. I have been checking logs and this is what I am seeing...

Normal:
220+*****************************
<server>
250-recipient_domain.com+
FROM:<sender@mydomain.com>+SIZE=96421
250+ok
TO:<recipient@their_domain.com>
250+ok
-
354+go+ahead
250+ok+1238075838+qp+73163+by+recipient_domain.com
-
221+recipient_domain.com+Goodbye.

Problematic:
220+***********************************************
<server>
250-recipient_server.com+Hello+my_server.com+[<my IP Address],+pleased+to+meet+you
FROM:<sender@mydomain.com>+SIZE=105099
250+2.1.0+<sender@mydomain.com>...+Sender+ok
TO:<recipient@their_domain.com>
TO:<recipient@their_domain.com>
TO:<recipient@their_domain.com>
250+2.1.5+<recipient@their_domain.com>...+Recipient+ok
-
354+Enter+mail,+end+with+"."+on+a+line+by+itself

And that is it, at this point, it moves on to the next mx record available. It seems that everything is working fine on our end, the attachment is a word document under 100K in size, nothing special about it. Any thoughts?

 

[dphantom]

Does your ISP use a smart host? From what I can tell, you should be good. This type of problem generally originates outside your network.