From: Mike Abraham (Mabrahamconestogac.on.ca)
Date: Wed Apr 02 2008 - 12:52:59 CDT

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Thank you for the response.

While this does describe the result, it is not the cause. I have come across this page several times.

It seems to be caused by the PIX firewall.

As soon as they turn off SMTP FIXUP PROTOCOL, it starts working fine.

I can't seem to convince everyone to turn off the FIXUP MAILGUARD function, so I need a Postfix workaround.

Mike Abraham

>>> On 4/2/2008 at 1:31 PM, mouss <moussnetoyen.net> wrote:
  Mike Abraham wrote:
> Am I ever glad I found this postfix group. I hope someone can help with
> this problem ?
>
> We are currently running postfix v2.2.10 with MAIA for Spam filtering.
>
> When some remote sites attempt to send email to us, they receive the
  following
> error:
>
> There was a SMTP communication problem with the recipient's email server.
> Please contact your system administrator.
> <EXCHANGE.Bluedrop.local #5.5.0 smtp;500 Non RFC-compliant response received>
>
  
  does this apply?
  http://smtp25.blogspot.com/2007/04/500-non-rfc-compliant-responses_18.html
  http://exchange911.org/cblog/index.php?/archives/27-500-Non-RFC-Compliant-respons
  e-received.html
  
> It always seems to be the sender has a EXCHANGE / PIX combination.
>
> The log produced from DEBUG_PEER on my POSTFIX server simply shows the peer
  suddenly drops the SMTP session for no reason.
>
> Has anyone found a solution or similiar situation with PIX firewalls causing
  a "Non RFC-compliant" error ?????
>
> Is there a workaround other can forcing the sender to disable SMTP FIXUP
  PROTOCOL on the PIX ? They don't always
> like this. Some admins refuse, saying it's our problem. Not there's.
>

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