Sending SMTP mail via mailx

[newbie]

I am confused on how mailx actually sends mail via SMTP ... and receive
the actual mail on Mozilla on windows2000.

1) What confuses me is that I have not told mailx ( or sendmail for that
matter ) the IP address or hostname of my ISP's SMTP server... but
somehow it did ... but based on the mail headers, it seems that it did
not actually forwarded the mail to my ISP's SMTP server, but it seems to
have figured out the MX record from the recipient's domain name, and
forwarded it straight to the recipient's domain name mail server.

Is this correct ? It seems to be the only explanation on how I actually
received the e-mail that I sent via mailx, without telling the box the
IP address of my ISP's SMTP server.


2) Doesn't mailx rely on a mail delivery agent / or mail transfer agent
to actually deliver the mail via SMTP ? ... like sendmail ?

[Anthony Mandic]

newbie wrote:

>
> I am confused on how mailx actually sends mail via SMTP ... and receive
> the actual mail on Mozilla on windows2000.
>
> 1) What confuses me is that I have not told mailx ( or sendmail for that
> matter ) the IP address or hostname of my ISP's SMTP server... but
> somehow it did ... but based on the mail headers, it seems that it did
> not actually forwarded the mail to my ISP's SMTP server, but it seems to
> have figured out the MX record from the recipient's domain name, and
> forwarded it straight to the recipient's domain name mail server.
>
> Is this correct ? It seems to be the only explanation on how I actually
> received the e-mail that I sent via mailx, without telling the box the
> IP address of my ISP's SMTP server.

You can easily find out your ISP's SMTP server by trying
"nslookup mailhost". If that doesn't work, run nslookup
interactively and then type "set type=MX" and then the
domain. You can also find a sendmail audit trail in
/var/log/syslog.

> 2) Doesn't mailx rely on a mail delivery agent / or mail transfer agent
> to actually deliver the mail via SMTP ? ... like sendmail ?

Yes, sendmail.

-am © 2003

[newbie]

Anthony Mandic wrote:

> newbie wrote:
>

>>I am confused on how mailx actually sends mail via SMTP ... and receive
>>the actual mail on Mozilla on windows2000.
>>
>>1) What confuses me is that I have not told mailx ( or sendmail for that
>>matter ) the IP address or hostname of my ISP's SMTP server... but
>>somehow it did ... but based on the mail headers, it seems that it did
>>not actually forwarded the mail to my ISP's SMTP server, but it seems to
>>have figured out the MX record from the recipient's domain name, and
>>forwarded it straight to the recipient's domain name mail server.
>>
>>Is this correct ? It seems to be the only explanation on how I actually
>>received the e-mail that I sent via mailx, without telling the box the
>>IP address of my ISP's SMTP server.

>
>
> You can easily find out your ISP's SMTP server by trying
> "nslookup mailhost". If that doesn't work, run nslookup
> interactively and then type "set type=MX" and then the
> domain. You can also find a sendmail audit trail in
> /var/log/syslog.

What I don't understand is ... in another network .... it gives the
following error:

----- Transcript of session follows -----
550 [email]josef.richard@xxxxxx.xx[/email]... Host unknown (Name server:
mailhost.xxxxxx.foo: host not found)


Why would it look for mailhost.xxxxx.foo ?


Same error appears in /var/log/syslog

>
>

>>2) Doesn't mailx rely on a mail delivery agent / or mail transfer agent
>>to actually deliver the mail via SMTP ? ... like sendmail ?

>
>
> Yes, sendmail.
>
> -am © 2003

So why is that, when I shutdown sendmail ( /etc/init.d/sendmail/stop ),
that mailx is still able to deliver SMTP mail ?

[Anthony Mandic]

newbie wrote:

> What I don't understand is ... in another network .... it gives the
> following error:
>
> ----- Transcript of session follows -----
> 550 [email]josef.richard@xxxxxx.xx[/email]... Host unknown (Name server:
> mailhost.xxxxxx.foo: host not found)
>
> Why would it look for mailhost.xxxxx.foo ?

Because "mailhost" is a default. Does that site have an MX record
when you do an ns lookup?

> So why is that, when I shutdown sendmail ( /etc/init.d/sendmail/stop ),
> that mailx is still able to deliver SMTP mail ?

Because it invokes it on the fly.

-am © 2003

[newbie]

Anthony Mandic wrote:

> newbie wrote:
>
>

>>What I don't understand is ... in another network .... it gives the
>>following error:
>>
>> ----- Transcript of session follows -----
>>550 [email]josef.richard@xxxxxx.xx[/email]... Host unknown (Name server:
>>mailhost.xxxxxx.foo: host not found)
>>
>>Why would it look for mailhost.xxxxx.foo ?

>
>
> Because "mailhost" is a default. Does that site have an MX record
> when you do an ns lookup?
>
>

>>So why is that, when I shutdown sendmail ( /etc/init.d/sendmail/stop ),
>>that mailx is still able to deliver SMTP mail ?

>
>
> Because it invokes it on the fly.
>
> -am © 2003

Thanks for the reply. I simply added mailhost into /etc/hosts:

10.0.10.52 mailhost.xxxxxx.foo


Last question:

Why does sendmail looks for mailhost.xxxxxx.foo ( why the .foo at the
end of the domain ) ? Why doesn't it use the domainname in
/etc/resolv.conf ?

There was no domainname entry in /etc/resolv.conf earlier, but I added
them, and sendmail still tries to look for mailhost.xxxxxxx.foo ?