Smarthost Failover - WAS RE: [Mimedefang] SMTP mailertable qu estion

[Cormack, Ken]

> Do you have to use ip addresses?  You cannot define two names the same
> way you defined two ip addresses?
> 
> define(`SMART_HOST', `host1:host2') 
> 
> Thanks

I thought about trying this too, but decided not to for the following
reasons.

First, the only references I have found in any documentation, including the
O'Reilly sendmail book (the "bat book") and the cf/README file included in
the sendmail source tree, only show the use of a colon in SMART_HOST, in the
context of

	"MAILER:hostname"

I would assume that any attempt to use hostnames here such as
"host1.domain.com:host2.domain.com" (as opposed to litteral IP addresses)
would be interperated by sendmail in this fashion

	If you cant figure out what to do with a messsage, forward
	it to "host2.domain.com", using the protocol/mailer known as
	"host1.domain.com".

Obviously, this would generate an "unknown mailer" error, since the standard
"mailer definitions" (smtp, esmtp, smtp8, uucp, relay, local and so on) do
not include a PROTOCOL called "host1.domain.com".

By using the brackets to enclose IP addresses, you immediately tell sendmail
"something is different here... this is an IP address... not a mailer name".
At which point, sendmail is apparently parsing the parameters to mean "try
the first IP address first, using the default mailer... then if that IP
address fails to respond, try the second IP address, again, using the
default mailer."

KEN CORMACK, RHCE
Sr. UNIX Systems Analyst,
    Open Systems Group
Sr. Software Analyst,
    TSG Midrange Systems Group
AFFILIATED COMPUTER SERVICES, INC.
    557 E. Tallmadge Ave., Akron, OH  44310
    mailto:kcormack at acs.roadway.com
    mailto:ken.cormack at acs-inc.com
    Phone: (330) 643-6372
    Fax: (330) 643-6367
    Pager: (800) 946-4646 Pin 1412819

"If that that is 'is' is that that is not 'not is', is that that is 'not is'
that that is not 'is'?  It is!" - Ken Cormack

"Sendmail administration is not black magic.  There are legitimate technical
reasons why it requires the sacrificing of a live chicken." - Unknown