Tom Strickland <[EMAIL PROTECTED]> wrote:
> ...
> I should have been more clear in my last posting: my main question was:
> If we're delivering our mail as coming from ourcharity.org.uk and it's
> being relayed through BT's (our new ISP) SMTP server, wouldn't it get
> blocked at some point by spam filters (e.g. on mailing lists, people's
> home machines)? Or have I misunderstood something?
The short answers:
Yes, but not by spam filters.
Maybe.
The long answer:
All *correctly configured* (see notes 1 and 2) ISPs these days have their
smtp servers set up to not relay mail. What does this mean? It means
that, if you connect to the smtp server (port 25) on their machine
then either you are from their domain or not. If you are inside
their domain(s) then you can send anywhere; if you are NOT from
inside their domain(s) then you can only send to recipients inside
their domain(s) (see note 3).
Huh? Well, if you connect to your isp (say, thatisp.uk), and tell them
you are ourcharity.org.uk then you are not sending from inside their domain
(probably - it depends upon exactly how they check your inside-ness!),
and thus you will only be able to send email to recipients whose email
addresses end in 'thatisp.uk' - probably not too useful. (See note 4)
However, if your firewall (or whatever) is set up as a 'smart smtp server'
(again, terminology from the 'old days' ;-), then everyone inside
ourcharity.org.uk would send email using THAT machine (which would
perform that relay test and see that you are sending email from INSIDE
ourcharity.org.uk and thus allow it). The 'smart smtp server' would
then send that email directly to the recipient machine, bypassing your
ISP's smtp server entirely. (Again, this is how I have mine set up,
and it works fine.) (Alternatively, you can just have the client
machines send directly to the recipient, but that's usually a quite
a bit more of a hassle).
There, clear as mud? ;-)
rc
Notes (perhaps more accurately called 'rabbit trails :-)
Note 1 - In the 'old days', 'correctly configured' meant that you
specifically DID allow mail relay, since that's how mail was sent!
(everything was via uucp, including mail, and so it was rare that both
ends of the email path were connected to the 'net at the same time,
so you HAD to 'relay' mail! Ah, the days of the old bang paths,
may they rust in peas! ;-) (Yes, I'm a 'net old-timer, aint it a
pain :-)
Note 2 - Nowadays, ALL correctly-configured smtp servers do not
do relaying of email. See also note 1 (;-)
Note 3 - I say 'domain(s)' instead of 'domain' because some SMTP
servers serve more than one domain.
Note 4 - In the old days, when I was a sysadmin, I used to test our
email config by sending mail out to an outside machine and then back to
myself. Once that was working, I'd then send it through *2* machines
outside and then back to myself. Using 'bang paths' that was trivial.
However, with '@' notation you have to do a little bit of what some might
consider trickery - since most smtp servers will do funny things nowadays
with 'bang' notation - you have to resort to '%' subnotation - but it only
works one level deep, unlike bang paths.... However, since all 'correctly
configured' smtp servers will not allow relaying (which you are doing using
'%' (and bang)), this is not useful any more... But it IS too bad that there
is no easy way to test email any more short of joining a mailing list and
sending it email!
Rusty E. Carruth Email: [EMAIL PROTECTED] or [EMAIL PROTECTED]
Voice: (480) 345-3621 SnailMail: Schlumberger ATE ___
FAX: (480) 345-8793 7855 S. River Parkway, Suite 116 \e/
Ham: N7IKQ @ 146.82+,pl 162.2 Tempe, AZ 85284-1825 V
ICBM: 33 20' 44"N 111 53' 47"W http://tuxedo.org/~esr/ecsl/index.html
