Sendmail/Exim and IP-Address

[George Toft]

Hi Roderick,

If you have control over some domain, say roderick.com, and you
want mail sent to roderick@roderick.com, which happens to be your
mail server at cpe-24-221-41-162.az.sprintbbd.net, you can set up 
a CNAME in your DNS MX records in DNS to reflect that.  Beware
the cautions of doing this in the DNS & BIND book.

Here's my domain:

$ dig @localhost georgetoft.com MX

; <<>> DiG 8.3 <<>> @localhost georgetoft.com MX 
; (1 server found)
;; res options: init recurs defnam dnsrch
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 3, ADDITIONAL: 3
;; QUERY SECTION:
;;      georgetoft.com, type = MX, class = IN

;; ANSWER SECTION:
georgetoft.com.         1D IN MX        10 mail.georgetoft.com.


If I were to replace my mx record with
cpe-24-221-41-162.az.sprintbbd.net,
my mail would be sent there.  Or, I could CNAME mail.georgetoft.com
with cpe-24-221-41-162.az.sprintbbd.net.  I just have to make sure
the box at the other end of cpe-24-221-41-162.az.sprintbbd.net is
set up to receive mail for georgetoft.com, and that port 25 is not 
blocked.

To get your mail server to send, you better have the IP address
resolve to roderick.com - that's the killer.  This is not to say
your mail server won't work, but it will not work with some ISP's
and mail centers.  I had this problem when I set up the data center
at a web hosting company.  I had to get the netblock owner (our 
ISP) to fix their arpa files.


Personally, I think you should spend $10/month on web hosting, and
use fetchmail to bring your mail to your local box.  That way, if 
there is any kind of disruption or IP change on your end, your mail 
will sit on the web host and wait for you.

Regards,

George

Roderick Ford wrote:
> 
> Hello,
> 
> I started looking into setting up an MX on my LAN, by reading info at
> Sendmail.org.  I have a fairly static IP address, i.e. not guaranteed to
> NEVER change, but never does.  It is VERY (34 char) long,
> "cpe-24-221-41-162.az.sprintbbd.net", and
> 
> (1) I'm wondering if mail sent here would have to be @this_long_address, or
> if there is a way to alias it shorter.
> (2) Will I be able to configure a mail server so that
>         (2a) fetchmail will forward retrieved mail to the mail server
>         (2b) where it can be retrieved by the user on the LAN?
> (3) Can the mail server be on the DNS server as long as they have the same
> name and don't slow each other down?
> (4) IF mail does have to go to webmaster@this_long_address, then it is over
> 40 characters...
>         (4a) too long?
>         (4b) Then mail will hit the router and be forwarded according to the
> port/firewall setting to the mailserver box, right?
> 
> Thanks,
> Rod
> 
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