Is this a Cisco PIX by any chance?
They're notorious for mangling SMTP connections.
Ronan Waide's [waider at waider.ie] 41 lines of wisdom included:
> Hi folks,
>> A little off-topic for ILUG, but.
>> I'm digging into a problem here that's making no sense. I've got a
> mail server sitting behind a Cisco which talks to the rest of the
> world via an ADSL line provided by eircom. At present, if I try using
> EHLO to any server anywhere, I get a 502 response. This obviously
> means I can't go pick up mail from my secondary MXs, because no EHLO
> -> no ETRN.
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