Re: Some email bounces = misconfigured exim?
On 16 Apr 1999, John Hasler wrote:
> George Bonser writes:
> > That would be ok provided:
>
> > 1. He never says HELO sympatico.com
>
> Why? His dynamic IP will resolve to the corresponding sympatico.ca
> hostname just as mine resolves to a win.bright.net one. I am
> elk-iqx2-cs-32.win.bright.net [208.149.150.158] right now. I say HELO
> win.bright.net right several times a day and it works just fine. As soon
> as his ppp connection comes up he has a valid address in the sympatico.ca
> domain.
That is fine because:
# nslookup
> set type=mx
> elk-iqx2-cs-32.win.bright.net
win.bright.net
origin = bucky.win.bright.net
mail addr = hostmaster.bright.net
serial = 9904120
refresh = 86400 (1 day)
retry = 14400 (4 hours)
expire = 3600000 (41 days 16 hours)
minimum ttl = 86400 (1 day)
In other words, the host you are saying in your HELO is a valid MX host
for your IP address. This will not work in his case unless there
is an MX record poiting to a hostname of sympatico.com that is a valid MX
host for the name his IP address reverse resolves to.
>
> > 2. All users on his box that can send outbound mail also have sympatico
> > accounts.
>
> Not necessary. There is no reason for there to be any relationship at all
> between the reverse-path and the address of the sender of the mail. In
> fact, only the domain name needs to be valid (and most isp's require that
> it be in their domain), though without a completely valid reverse-path you
> may not always get bounced mail back.
Yes there is if you ever want a bounce to get to the right place. Bounce
messages use the envelop sender, not the From: or Replay-To:
>
> > 3. All users have exactly the same username on his box as the sympatico
> > email address.]
>
> The username in the reverse path doesn't have to be a valid sympatico email
> address. Sympatico will just verify the domain and ignore the rest.
When their root@sympatico.com mailbox starts filling with bounce messages
or their double-bounce message box starts collecting things, they might
notice.
Also, what happens when you want to send mail at another sympatico.com
user that is not on your box? You will need to set up a luser relay.
It is just a BAD IDEA to try to make your box think it is your ISP.
>
> If you wanted to, you could extract the FQDN of your current dynamic IP
> connection from /var/log/ppp.log, stick "postmaster@" or "root@" on the
> front, and edit your MTA config to use that as a reverse-path.
No, it is better to use a visible name ofg a valid MX host for your IP
address, MOST mailers will accept that, some will not.
> But genkin@sympatico.ca is his valid email address. If all users on his
> system use that as a reverse-path the worst that will happen is that he
> will get their bounces in his mailbox at sympatico, exactly what he wants.
> If he uses qwerty@sympatico.ca, or genkin@qwerty.sympatico.ca then the
> worst that will happen is that some returned mail will go in the bit
> bucket.
No that is NOT what will happen. If user foo sends mail, a bounce will try
to go to foo@sympatico.com which might not exist. To try to hack ALL
senders to one address is foolish. It is a lot easier to do it right.
Just send the mail through the ISP's mail server instead of trying to
deliver it direct. It will save you a LOT of bandwidth.
THere is also no need for a staic IP. Using a service such as dhs you can
map a hostname (which is free) to your dynamic IP address.
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