421 SMTP service not available, closing transmission channel

[John Salfer]

Hello,

We have a linux and an SCO box running for mail services. Configuration is
the Linux box is used for all outgoing mail from client PC's and mail is
picked up from the SCO box. Mail from the internet is received into the SCO
box as well.

In-house client PC's sending mail to an outside address works great, but
sending to local users (on the SCO box) don't get forwarded. While looking
into the problem using telnet from the linux box to connect to the SMTP
server it connects as expected through the intranet, but not when the public
domain name is entered, it states the 421 message. When connecting offsite
from other domains on the internet SMTP works fine into the SCO box. See
below for example. When the smart host entery in sendmail.cf is changed to
DSintranet.ip.hostname local mail is forwarded to the SCO box and delivered
like we want, but mail destined to addresses outside our domain get stuck in
the Linux boxes mail queue. DH is set for intranet.ip.hostname.

--------
linux_box # telnet internet.ip.hostname 25
Trying 2.1.2.1... (ip changed to protect the innocent)
Connected to 2.1.2.1.
Escape character is '^]'.
421 SMTP service not available, closing transmission channel
Connection closed by foreign host.

linux_box # telnet intranet.ip.hostname 25
Trying 192.168.10.2...
Connected to intranet.ip.hostname.
Escape character is '^]'.
220 intranet.ip.hostname ESMTP Sendmail ready at Mon, 29 Apr 20
02 16:03:56 -0500 (CDT)
quit
221 intranet.ip.hostname closing connection
Connection closed by foreign host.
-----------

I must have something configured incorrectly somewhere.

Ideas would be greatly appreciated.
John.
jo...@cdsmn.com

[Neil W Rickert]

"John Salfer" <jo...@voyageursw.com> writes:

>linux_box # telnet internet.ip.hostname 25
>Trying 2.1.2.1... (ip changed to protect the innocent)
>Connected to 2.1.2.1.
>Escape character is '^]'.
>421 SMTP service not available, closing transmission channel
>Connection closed by foreign host.

This appears to be your ISP blocking outbound SMTP.

Try setting your ISP mail server as your SMART_HOST

[John Salfer]

ISP would charge if their SMTP server is used.

Other mail is making it to it's destination. Only local mail destined for
the SCO box is getting stuck.

My feeling is it's a networking thing being the Linux and SCO box on the
same network (192.168.10.0). The sendmail on Linux box is attmpting to use
the public IP instead of the local address.

Can sendmail be configured to watch for mail with a particular destination
and forward it to the SCO box? I imagine this is easier said than done.
John.

"Neil W Rickert" <ricke...@cs.niu.edu> wrote in message
news:aaklsc$bvj$1...@husk.cso.niu.edu...