554 is the universal error for "invalid command arguments." The leading "5" indicates the error is permanent. If the leading digit was a "4" that would indicate a temporary error.
In the case of the additional information supplied with your "554" error, it appears that the receiving server is stipulating that the "invalid command argument" is caused by the fact that the reason the message was bounced is because it was found in one of their spam databases.
This error message is becoming a much more frequent occurrence as more and more MX server operators choose not to return an actual bounce message because sending out too many bounce messages gets mail server operators added to "back scatter" databases, which also causes mail delivery to be blocked.
Here's MIT's official response to why they issue "not allowed" codes. As you will see, it covers a variety of reasons, all of which can be frustrating to troubleshoot:
To help you understand what they might be bouncing you for, check your spam reputation and also send a message to MAILTEST@UNLOCKTHEINBOX.COM.
Henry's testing server will send back an analysis of your DNS and mail server configuration which may prove helpful in figuring things out.
You can also test at both of these places:
Good luck tracking this down.
Bruce Barnes
ChicagoNetTech Inc
brucecnt@comcast.net
Phonr: (773) 491-9019
Phone: (224) 444-0169
E-Mail and DNS Security Specialist
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