The following configuration enables VERP (http://cr.yp.to/proto/verp.txt) which is useful for mailing list managers that are able to take advantage of that feature.
This configuration is currently used for using the mlmmj manager with VERP enabled + sendmail.
The hack consists in hooking VERP rewriting in a replacement ruleset for the existing EnvFromSMTP one (called VerpEnvFromSMTP). This is going to work *only* if we are splitting messages with multiple recipients in separate queue files since the macro we are using for the rewriting ($u) is not set when multiple rcpt are present.
The first step consists in forcing envelope splitting, this is done using the QUEUE_GROUP feature, here we are definining r=1 (max 1 rcpt per message) for the default queue group:
QUEUE_GROUP(`mqueue', `P=/var/spool/mqueue, F=f, I=1m, R=2, r=1')
Since we are going to split a lot it's advisable to use the FAST_SPLIT option, additionally we need to enforce return-path inclusion in the local mailer:
define(`confFAST_SPLIT', `100')dnl define(`LOCAL_SHELL_FLAGS', `eu9P')dnl
Then we define a regex map for matching the addresses that we are going to rewrite, in our example we'll rewrite addresses like
<listname+bounces-123@domain.net>
with
%lt;listname+bounces-123-user=foo.net@domain.net>
where user@foo.net is the recipient address of the message. So we need to apply
our verp ruleset *only* to those addresses. Additionally we are also adding the
Delivered-To header:
LOCAL_CONFIG Kmatch_verp regex -m -a@VERP (listname\+bounces\-[0-9]+<@domain\.net\.?>) H?l?Delivered-To: $u
Here's the ruleset, the first half of the ruleset is the existing EnvFromSMTP ruleset present in default sendmail.cf, the seconf half is the VERP stuff:
SVerpEnvFromSMTP R$+ $: $>PseudoToReal $1 sender/recipient common R$* :; <@> $@ list:; special case R$* $: $>MasqSMTP $1 qualify unqual'ed names R$+ $: $>MasqEnv $1 do masquerading R $* $: $(match_verp $1 $) match the address R $* + $* < @ $* . > $* @VERP $: $1 + $2 - $&u < @ $3 . > $4 VERP rewrite it using $u macro and add VERP string for failsafe R $* - < @ $* . > $* VERP $: $1 < @ $2 . > $3 if $u wasn't defined rewrite the address back R $* - < $+ @ $+ > < @ $* . > $* VERP $: $(dequote $1 "-" $2 "=" $3 $) < @ $4 . > $5 replace the "@" in rcpt address with "=" R $* - $+ @ $+ < @ $* . > $* VERP $: $(dequote $1 "-" $2 "=" $3 $) < @ $4 . > $5 replace the "@" in rcpt address with "="
Finally we need to rewrite the mailer definition for the used mailer (typically esmtp) specifying VerpEnvFromSMTP as the sender rewrite ruleset:
MAILER_DEFINITIONS
Mesmtp, P=[IPC], F=mDFMuXa, S=VerpEnvFromSMTP/HdrFromSMTP, R=EnvToSMTP, E=\r\n, L=990,
T=DNS/RFC822/SMTP,
A=TCP $h
NOTE: for mailing list servers it's also a good idea keeping existing Delivered-To headers, sendmail needs the following patch for doing this