Re: [client] did not issue MAIL/EXPN/VRFY/ETRN during connection

HQuest wrote:

So there is some "screwup device" in front of sendmail?
It's broken, get rid of it.
220 ***************************************************
That's an obvious violation of the RFC:
   Greeting       = ( "220 " (Domain / address-literal)

Odd - the obfuscation ("Mask server banner") is shown as disabled, but still being enforced. Can confirm via a packet capture from the external border router.

Seems everywhere I look I find new security appliances. We identified the one with the obfuscation feature enabled and managed to get approval for disabling it. I still don't receive emails from Proofpoint, but this have fixed delivery issues with another provider (Mailchimp). Acceptable or not (as per a separate brief discussion), this is now up to our IS group to decide if a working solution outweigh their paranoia.
I'll continue to dig into this, now with some technical help from other manufacturers. The last bug search has raised many concerns.