BDAT 500 Syntax error to just 1 user?

[nolacoaches]

Using Xwall with an Exchange 55 server. When sending the same message to 2 different users at the same site, 1 suceeds, 1 fails. The Xwall log shows the same sequence of events up to the BDAT xxxx LAST statement. The sucessful user replies 250 Requested mail action okay, completed. The failed user replies 500 Syntax error, command unrecognized. They are both on the same mail server. I'm guessing it's something in their firewall, any suggestions about what to look for?

Never stay up on the barren heights of cleverness, but come down into the green valleys of silliness.
Ludwig Wittgenstein

 

[nolacoaches]

Found sort of an answer on my own from XWALL (I use XWALL spam filter). Firewalls with an SMTP Proxy frequently do not handle ESMTP commands like BDAT properly. Sometimes they corrupt the size parameter following the BDAT command making subsequent data appear garbled and incorrect.

XWALL suggests 2 solutions: a) turn of the firewall SMTP Proxy, or b) reduce the efficiency of XWALL by either disabling ESMTP or unchecking "CHUNKING".

I can't control the user's firewall, so I unchecked "CHUNKING" and seems to be working so far.

Never stay up on the barren heights of cleverness, but come down into the green valleys of silliness.
Ludwig Wittgenstein