Postfix (virtual users) + dovecot + sieve: envelop does not contain original recipient

Question

I have set up my email server following the ISPMail tutorial with virtual users in postfix + dovecot + sieve. My problem is: the envelop "variable" in sieve does not contain the original recipient.

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I have a mail account, let's call it [email protected] and additional aliases set up for postfix which all deliver to the aforementioned address:

[email protected] -> [email protected]
@domain.com -> [email protected]

The latter being an catch-all address.

Postfix calls dovecot with the following config line in master.cfg:

dovecot   unix  -       n       n       -       -       pipe
  flags=DRhu user=vmail:vmail argv=/usr/lib/dovecot/dovecot-lda -f ${sender} -d ${user}@${nexthop} -a ${recipient}

With sieve I want to put all mails received for the catch-all address into a specific folder. My sieve code looks like this:

if envelope :is :domain "To" "domain.com" {
  fileinto "special-folder";
}

This sadly does not work. Digging further I found out that what's inside envelop always is the final delivery address, i.e. [email protected] in this case. I found this using the following rule:

if envelope :matches "To" "*" {
  fileinto "${1}";
}

And the sieve log telling me:

failed to store into mailbox '[email protected]': Mailbox doesn't exist: [email protected].

I'm already guessing that this has to be a problem somewhere between postfix and dovecot as the mail log tells me the following:

Aug 29 10:38:27 *** dovecot: lda([email protected]): sieve: msgid=<54003C01.1080704@***>: stored mail into mailbox 'INBOX'
Aug 29 10:38:27 *** dovecot: lda([email protected]): Error: sieve: execution of script /var/vmail/example.org/mail/dovecot.sieve failed, but implicit keep was successful (user logfile /var/vmail/example.org/mail/dovecot.sieve.log may reveal additional details)
Aug 29 10:38:27 *** postfix/pipe[12469]: A31A28006B: to=<[email protected]>, orig_to=<[email protected]>, relay=dovecot, delay=0.29, delays=0.18/0.01/0/0.1, dsn=2.0.0, status=sent (delivered via dovecot service)

Obviously postfix states the original recipient ([email protected]) and the mailbox delivered to ([email protected]) but somehow this information gets lost on the way to dovecot?!

Answer 1

This behavior happened because you add {recipient} macro in dovecot-lda argument. As stated in man pipe, the postfix will replace that macro with final recipient (mail.example.org) instead of not original ones ([email protected]).

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Instead of parsing envelope, you can parsing another header like X-Original-To. This header intended to preserve the original recipient before rewriting or aliasing. To enable this header, edit master.cf so the dovecot line become (notice that flag argument was edited)

dovecot   unix  -       n       n       -       -       pipe
  flags=DROhu user=vmail:vmail argv=/usr/lib/dovecot/dovecot-lda -f ${sender} -d ${user}@${nexthop} -a ${recipient}

Then your sieve script become

if header :matches "X-Original-To" "*" {
  fileinto "${1}";
}

A bit complicated but the result is you can have original recipient and its aliases.

Answer 2

After some testing (the answer by masegaloeh and the help of a friend provided some useful hints) there are two ways (both seem to work equally good):

1. Use ${original_recipient} instead of ${recipient}:

   As man pipe tells us "This macro expands to the complete recipient address before any address rewriting or aliasing" so it is the solution to my problem. So the modified command line in master.cf should look like

   dovecot   unix  -       n       n       -       -       pipe
     flags=DRhu user=vmail:vmail argv=/usr/lib/dovecot/dovecot-lda -f ${sender} -d ${user}@${nexthop} -a ${original_recipient}
   

2. Use a X-Original-To header an tell dovecot to set its envelope to this header field:

   As masegaloeh suggested I add O to the flags telling postfix to add the X-Original-To header. Inside /etc/dovecot/conf.d/15-lda.conf I tell dovecot to use this header for its envelope:

   lda_original_recipient_header = X-Original-To
   

   As the comment above this config options tells us, we must not use the -a option when calling dovecot-lda via postfix because it overrides this setting. Thus the master.cf looks like:

   dovecot   unix  -       n       n       -       -       pipe
     flags=DORhu user=vmail:vmail argv=/usr/lib/dovecot/dovecot-lda -f ${sender} -d ${user}@${nexthop}