Paul Cocker wrote:
The primary passes to an internal mail server, but performs recipient
validation before doing so. This is why I don't believe it's worth doing
on the secondary because it means genuine recipients will be checked
with the internal server twice (should they be received by the
secondary, not primary MX).
Let's go the concrete example way.
$ host -t mx jonview.com
jonview.com mail is handled by 10 mx.ca.mci.com.
jonview.com mail is handled by 5 mail.jonview.com.
so the domain has a primary and a secondary (and the primary probably
passes mail to an internal server as suggested by the "user unknown in
RELAY recipient..." below).
now here's a bounce from yesterday junkscatter storm:
This is the mail system at host mx03.ca.mci.com.
...
<[EMAIL PROTECTED]>: host mail.jonview.com[209.47.92.183] said:
550 <[EMAIL PROTECTED]>: Recipient address rejected:
User unknown in relay recipient table (in reply to RCPT TO command)
...
so the primary does recipient validation and the secondary sent me the
junk (the original subject was "5% off for 305.mattias1". I guess you're
now familiar with such subjects).
ALL servers that get connections from strangers MUST do recipient
validation DURING THE SMTP TRANSACTION. you get your share of junk, I
get mine, and I get enough of it, so I don't need to see yours.
PS. when you post, fix the subject line by removing the silly "spam" tag
added by your (broken?) filter.
Also please do not top post. put your replies after the text you reply
to. google if this is not clear.
Apologies if my terminology is off here. I always think of MX servers as
gateways, though I realise in some companies the gateway server and the
internal mail server will be one and the same.
From reading further into your response, perhaps I misunderstanding MX
records. So far as I know, if the secondary MX server receives the
e-mail, it shouldn't pass it inside but rather should pass it to the
primary MX server, which should be the single point of contact with the
internal mail server. Is this incorrect?
That's ok. but you can easily understand that ratware doesn't care about
the standards. Some ratware intentionally skips the first MX. See
Jorey's nolisting page:
http://nolisting.org/
