another DNS problem

[Garry T. Williams]

On Saturday, October 30, 2010 22:30:40 Kevin J. Cummings wrote:
> On 10/30/2010 06:16 PM, Hiisi Troll wrote:
> > In the provided sendmail.mc file there's an option:
> > define(`SMART_HOST', `smtp.direct.ru')dnl I thought it relays all
> > my outgoing mail to ISP smtp server. Or am I wrong here?
> 
> Try putting the smtp machine name between square brackets:
> 
> define(`SMART_HOST', `[smtp.direct.ru]')dnl
> 
> there is something about the square brackets and its use to either
> use or keep sendmail from using the MX or an A record instead for
> the listed host (sorry, I can't remember the details, only that it
> works!).  I use it (the square brackets) for my ISP's smtp server
> and I can send email out through it.

The meaning of SMART_HOST is the *MX* host for the name.  In other
words, sendmail will look up the MX record for smtp.direct.ru to find
out what host to connect to.

The MX record *could* specify another host -- not smtp.direct.ru .
(In this case, there is no MX record for smtp.direct.ru so its A
record will be used, which is what you want.)  My ISP's relay host
does specify a different host for its MX.  That host refuses relay
from my IP address.

To specify a host address instead of the MX host for a domain, place
the host address inside of square brackets as Kevin states above.  Now
even if an MX record someday shows up for that domain name
(smtp.direct.ru), its A record will still be used.

-- 
Garry T. Williams