ESMTP Verbs not rendered correctly - 250-XXA

Source: Microsoft Support

RAPID PUBLISHING

RAPID PUBLISHING ARTICLES PROVIDE INFORMATION IN RESPONSE TO EMERGING OR UNIQUE TOPICS, AND MAY BE UPDATED AS NEW INFORMATION BECOMES AVAILABLE.

Mail between RGs is slow to non existent and sometimes the queues go into retry states.

Mail flow can be affected both ways and sometimes only one way RGs are connected via VPNs.

Telnet to server that is in retry state and ehlo returns:

Netmon caps show OD OA in packet but not the completition of a second OD OA to signify the completion of the message. We never see the Fin sent or received. There is a 625+ second delay before we time the connection out.

CISCO Router filtering and then dropping what it deems as 'invalid SMTP command' packets. See resolution below for more information

Contacting CISCO to check configuration of the Firewall for SMTP
CISCO removing firewall feature set for testing
CISCO says it was logging an invalid SMTP command
ESMTP verbs cleaned up now
All mail dequed

The CISCO Feature set provides "Firewall like" features to inspect packets and prevent "abnormal" packets from being transmitted. The feature set does a stateful inspection of the packets looking for the abnormal packets and block these. In the log it was showing an invalid SMTP command