Re: [Exim] HELO syntax check

On Wed, 21 Aug 2002 14:28:30 +0100 (BST) Chris wrote:

> Exim checks the syntax of HELO and EHLO commands for incoming SMTP
> mail, and gives an error response for invalid data
> which I suppose it does. But this is hardly rejecting the mail.
> Shurely it needs to 550 every subsequent RCPT command ?

I remember having a similar issue not so long ago and reading up on it.
I'm pretty sure there's something somewhere (in an RFC? Or maybe somewhere
in the Exim docs?) that says the MTA/Exim should/does still accept the
mail as normal following a 501 related to a HELO (even in the absence of a
valid HELO) but for the life of me I can't currently find what it was that
I was reading. All I can find at the moment is a bit in RFC821 which says
the MTA should stay in the "same state". Without reading in more detail
(I'm sure Phil will know offhand) I can't say whether a HELO is actually
*required* or whether it's optional. If the latter, that would explain it,
although even if the former it might be explained by a 'liberal' policy in
Exim on accepting stuff (since realistically the HELO is rarely relied on
for much).

I set 'helo_accept_junk_hosts = *' after being attacked by a seriously
broken (Microsoft, surprise surprise) MTA which was sending some junk
(i.e. syntactically invalid) HELO header, but then on receiving a 501
disconnected, then 1 second later reconnected and retried with the same
broken HELO, ad infinitum. *wrings necks of terminally stupid MS coders*


Tim