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Re: SMTP standards : needs outgoing SMTP server be MX for my domain?

	This could be an internal policy decision on their part... In
which case I would assume that the proper response back would be an
x.7.1 which states it's policy... Either 4.7.1 if it's not fatal or
5.7.1 if it is... 

	There is nothing that I am aware of that stipulates what an MTA
administrator can and can not set as internal policy for mail they are
willing to receive... In fact I'm in the process of designing a Sendmail
milter for our network at work to enforce the policies we're putting
into place... One idea for it is to actually lookup the MX server for
the incoming domain and very the FROM address really is valid... Now if
everyone accepted VRFY this would be easy but is not the case thanks to
spammers which have caused many MTA admins to turn that feature off... 

	Another simple way to catch many spammers is to actually check
the HELO arguments and either later reject the message or just discard
it if the argument is not either 1) a valid FQDN, 2) domain name or 3)
IP address in proper notation... I've found many spammers just sending
random characters, as well as yahoo.com, hotmail.com, etc are popular
and even a few give my MTA my MTA's own IP address... 

	Internal policy is internal policy and you can't really twist
their hand to change it... 


On Wed, Dec 18, 2002 at 04:08:59PM +0100, DEFFONTAINES Vincent wrote:
> An organization refuses emails from my domain, under this reason :
> My domain's mailer that connects to their SMTP server is not MX of my
> domain.
> Indeed it is not, I have different hosts for ingoing and outgoing email
> traffic.
> Actually, I see no good reason why outgoing mailer should be the same as MX.
> I am wondering if SMTP standards require that email sender of a domain be
> its MX? I find that really surprising.
> I'll be glad to know if anyone can enlight me.
> Thanks,
> Vincent
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