Using IP addresses in mailertable

It is possible to specify IP addresses instead of hostnames or MX records as the destination in the Sendmail mailertable. I only recommend using this as a temporary solution when you cannot wait for a DNS change to take effect.

When specifying a destination IP address, make sure the IP address is surrounded by brackets. The following mailertable entry will fail:

brandonhutchinson.com    esmtp:207.139.9.68

Nov 22 13:56:28 host sendmail[9902]: gAMJuRQE009902: to=brandonhutchinson@hotmail.com, ctladdr=user(65536/1), delay=00:00:01, xdelay=00:00:01, mailer=relay, pri=30000, relay=localhost.host.com. [127.0.0.1], dsn=2.0.0, stat=Sent (gAMJuRin009903 Message accepted for delivery)
Nov 22 13:56:28 host sm-mta[9907]: gAMJuRin009903: to=<brandonhutchinson@hotmail.com>, ctladdr=<user@host.com> (65536/1), delay=00:00:01, xdelay=00:00:00, mailer=esmtp, pri=120322, relay=207.139.9.68, dsn=5.1.2, stat=Host unknown (Name server: 207.139.9.68: host not found)

The correct mailertable entry:

brandonhutchinson.com    esmtp:[207.139.9.68]

Nov 22 13:57:09 host sendmail[10054]: gAMJv9l0010054: to=brandonhutchinson@hotmail.com, ctladdr=user (65536/1), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30000, relay=localhost.host.com. [127.0.0.1], dsn=2.0.0, stat=Sent (gAMJv9in010055 Message accepted for delivery)
Nov 22 13:57:46 host sm-mta[10058]: gAMJv9in010055: to=<brandonhutchinson@hotmail.com>, ctladdr=<user@host.com> (65536/1), delay=00:00:37, xdelay=00:00:37, mailer=esmtp, pri=120322, relay=[207.139.9.68] [207.139.9.68], dsn=2.0.0, stat=Sent (TAA05224 Message accepted for delivery)

What if we want to use an IP address as the key in the mailertable, rather than the value? For example, one of our mail relays (relay 1) attempted to deliver mail to user@[IP_address] (including the brackets around the IP_address). The mail server at IP_address is only reachable on relay 2.

Mailertable apparently does not accept an IP address with the [IP_address] key value. I also was not able to create a [IP_address] VirtHost for use with the virtusertable.

To route user@[IP_address] mail from relay 1 to relay 2, I had to:

1. Add [IP_address] to class w on relay 1.
2. Create an aliases database entry on relay 1:
user:   user@relay_2
3. Create an aliases database entry on relay 2:
user:    user@[IP_address]

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Last modified: 05/06/2003