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Re: RFC 5321bis / 2821ter

2009-01-27 06:26:26

Alessandro Vesely wrote:
Paul Smith wrote:
If they have SBS set up correctly then it should just work. 

Under the 'current' way yes, but if it is changed so that the EHLO
parameter must correspond to the IP address of the sending host, then
it won't work, and I can't think of anything which would make it work.

May I ask how can that server receive any responses to the mail it sends?
You must have missed the bit where I said it uses the Exchange POP3
connector to collect mail from the ISP's server.

It would HAVE to go via a third party smarthost, many of these are
unreliable and/or slow, so people prefer not to use them if they can.
It is not possible to define a possible set up, until the 'next' HELO
parameter has a definitive wording. The general tendency is to use the
DNS for storing that information, i.e. operative records (A, MX) if at
all possible, declarative records (SPF, TXT) otherwise. Assuming that,
dynamic DNS is the only way, unless the dynamically assigned address
varies within a reasonably small pool that is established beforehand.
What I am cautious about is making changes to SMTP which will make
sending for legitimate senders more difficult without major improvements
to stopping bad senders. Changing the HELO parameter to add new
requirements to it just seems to make it more difficult for legitimate
senders without doing anything to stop bad senders.

The HELO/EHLO parameter means nothing. It has no relationship to the
MAIL FROM domain, or to anything the recipient of the message sees. You
can't possibly do an SPF check on the EHLO parameter, and expect it to
mean anything. All you can do is check to see if the EHLO parameter
resolves to the IP address of the sending host, and that tells you
nothing except the sender has set it up correctly... Spammers can set up
domains & mailing software correctly more easily than the majority of
legitimate users can.

Paul Smith

VPOP3 - POP3/SMTP/IMAP4/Webmail Email server for Windows

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