Mail Server Configuration

For sendmail 8.9.x and later versions, add the following to your .mc file under LOCAL_CONFIG...

# dynamic relay authorization control map
Kdrac btree /etc/mail/dracd

and the following under LOCAL_RULESETS...

SLocal_check_rcpt
# allow recent POP/IMAP mail clients to relay
R$*				$: $&{client_addr}
R$+				$: $(drac $1 $: ? $)
R?				$@ ?
R$+				$@ $#OK

If you are using the DUL to block connections from dial-up IP addresses, you will need to add the same four rules to the SLocal_check_relay ruleset in your .mc file to allow DRAC-authenticated users to connect.

Tabs are required between the two sides of these rules!

Then, you can re-make the .cf file, install it, and restart the sendmail SMTP daemon. Please don't edit your sendmail.cf file directly. Regenerating it from the .mc files is a much safer procedure.

Mike McHenry contributes the following information for a complex sendmail configuration...

I have some updated sendmail rules for sendmail 8.11.0 that may or may not help people out. These rules are tuned for a full email server running all of the relay checks and spam filtering features of the new sendmail. First I will include an example sendmail.mc file and then I will show where the drac configs need to be manually patched in to the resulting sendmail.cf file.

EXAMPLE MC FILE:
OSTYPE(`linux')dnl
define(`confAUTO_REBUILD')dnl
define(`confCONNECTION_RATE_THROTTLE',40)dnl
define(`confMAX_HOP',30)dnl
define(`confMAX_MESSAGE_SIZE',10000000)dnl
define(`confPRIVACY_FLAGS',`authwarnings,needmailhelo')dnl
define(`confQUEUE_LA',5)dnl
define(`confREFUSE_LA',10)dnl
define(`confTO_CONNECT', `1m')dnl
define(`confTO_IDENT',0s)dnl
define(`confTO_QUEUEWARN', `12h')dnl
define(`confTRY_NULL_MX_LIST',true)dnl
define(`STATUS_FILE',`/etc/mail/sendmail.st')dnl
define(`ALIAS_FILE',`/etc/mail/aliases')dnl
FEATURE(`smrsh',`/usr/sbin/smrsh')dnl
MAILER(`smtp')dnl
FEATURE(`local_procmail', `/usr/bin/procmail')dnl
FEATURE(`always_add_domain')dnl
define(`MASQUERADE_NAME',`domain.com.')dnl
FEATURE(`limited_masquerade')dnl
define(`confCW_FILE',` /etc/mail/sendmail.cw')dnl
FEATURE(`use_cw_file')dnl
FEATURE(`accept_unresolvable_domains')dnl
FEATURE(`redirect')dnl
FEATURE(`virtusertable',` hash -o /etc/mail/virtusertable')dnl
FEATURE(`access_db')dnl
FEATURE(`blacklist_recipients')dnl
FEATURE(dnsbl, `rbl.maps.vix.com', `Rejected - see
http://www.mail-abuse.org/rbl/')dnl
FEATURE(dnsbl, `dul.maps.vix.com', `Dialup - see
http://www.mail-abuse.org/dul/')dnl
FEATURE(dnsbl, `relays.mail-abuse.org', `Open spam relay - see
http://www.mail-abuse.org/rss/')dnl

LOCAL_CONFIG
# dynamic relay authorization control map
Kdrac btree -o /etc/mail/dracd

Manually patch into the resulting sendmail.cf the following chunks of code:

At the END of SLocal_check_rcpt right before the last "catch-all" reject insert the following chunk of code (ignore the final reject code that follows the DRAC code chunk)...

# allow recent POP/IMAP mail clients to relay
R$*                     $: $&{client_addr}
R$+                     $: $(drac $1 $: ? $)
R?                      $:
R$+                     $@ RELAYFROM

# anything else is bogus
R$*                     $#error $@ 5.7.1 $: "550 Relaying denied"

Also, if you are making use of the MAPS DUL lists you will need to add a check for DRAC in SBasic_check_relay to allow your customers to relay mail even if they are coming from a dialup outside of your control. Add the following before the first MAPS checks in the sendmail.cf (ignore the MAPS lines following the DRAC code chunk)...

# allow recent POP/IMAP mail clients to relay
R$*                     $: $&{client_addr}
R$+                     $: $(drac $1 $: ? $)
R?                      $:
R$+                     $@ RELAYFROM

# DNS based IP address spam list rbl.maps.vix.com
R$*                     $: $&{client_addr}

That's it! Fine-tune to suit your needs and restart sendmail.

For Postfix, here is a sample relay mapping, contributed by Jeff Johnson...

myhostname = mail.________.com
mydomain = ________.com
mydestination = $myhostname, localhost.$mydomain, $mydomain, mail.$mydomain,
ns1.$mydomain
relay_domains = $mydestination
smtpd_recipient_restrictions = permit_mynetworks, check_client_access
btree:/etc/mail/dracd, check_relay_domains