# [EMAIL PROTECTED] / 2006-10-12 11:23:52 -0500:
> On Wed, October 11, 2006 11:28 pm, Peter Lauri wrote:
> > [snip]
> > Unless the email is coming "from" somebody the recipient knows/trusts,
> > then you're going to get marked by them as a spammer -- which will
> > report back to some of the lists marking you as a spammer.
> > [/snip]
> >
> > But is it not a problem sending from the SMTP server thedomain.com
> > using something else then the email [EMAIL PROTECTED] I am
> > planning to send from an existing email from the domain.
>
> Not really -- at least not in my limited experience.
>
> There are so many OTHER factors that the DNS resolution of the return
> address and the actual SMTP machine not matching up are probably not a
> deciding factor...
Sender, client.example.org, IP 1.2.3.4 connects to the receiver
(server.example.org).
1. DNS - PTR RR. If 4.3.2.1.in-addr.arpa doesn't exist (the value
would be client.example.org), server refuses the connection
2. DNS - A RR. If client.example.org doesn't exist or doesn't
resolve to 1.2.3.4, server refuses the connection
3. DNS - RBL. If 1.2.3.4 is in any of a number of possible
RBLs, server refuses the connection
4. DNS - RHSBL. If example.org is in any of a number of possible
RHSBLs, server refuses the connection
If the client passed all checks, the server accepts the connection:
S: 220 server.example.org ESMTP
C: HELO client.example.org
S: 250 Ok
5. SMTP - If client doesn't say HELO with a FQDN argument, or
6. SMTP - If the HELO command argument doesn't resolve to the client
IP address, the server responds with a 4xx or 5xx.
C: MAIL FROM: [EMAIL PROTECTED]
7. DNS - MX or A RR. If neither of these records exists for
elsewhere.org, server replies with 5xx, permanent error.
S: 450 Greylisted
C: QUIT
server replied with a 4xx temporary error code, the client (rightly)
disconnected. server in turn tries to send a message back to
[EMAIL PROTECTED] to see if it accepts email:
E: 220 erwin.elsewhere.org ESMTP
S: HELO server.example.org
E: 250 Ok
S: MAIL FROM: <>
E: 250 Ok
S: RCPT TO: <[EMAIL PROTECTED]>
E: 250 Ok
S: QUIT
The empty FROM address is the special null address used to send
bounce messages.
Should erwin reply with 5xx to any of the commands from server,
[EMAIL PROTECTED] will be stored in a nondeliverables database, and
when client returns it'll be rejected:
C: MAIL FROM: <[EMAIL PROTECTED]>
S: 550 Sender rejected
I'm sure I forgot something or screwed the description here and
there, but you get the idea.
--
How many Vietnam vets does it take to screw in a light bulb?
You don't know, man. You don't KNOW.
Cause you weren't THERE. http://bash.org/?255991
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