Cyrus - Exim4 configuration

1. Use Exim version 4. Exim version 3 just doesn't cut it in the lmtp area, which is very important for performance when dealing with Cyrus IMAPd.

2. Acá yo creo un archivo que se llama conf.d/transports/31_exim4-config_cyrus21-imapd y pongo lo dice acá.

  Use the LMTP transport to deliver using a unix socket (fastest), or the SMTP transport in LMTP mode to deliver over a TCP/IP socket.

  For local delivery over a unix socket, add a file into conf.d/transports with the following:

cyrus_delivery:
      driver = lmtp
      socket = /var/run/cyrus/socket/lmtp
      batch_max = 20
      user = mail

  (set batch_max to whatever is best for your setup, and make sure you allow enough Cyrus lmtp processes to serve that many lmtp connections)

  If that doesn't work, I suggest you create a group for lmtp delivery, add whichever user exim is running as to it, and use dpkg-statoverride to make /var/run/cyrus/socket/lmtp writeable by that group.

  To then deliver to Cyrus, you will need to comment check_local_user in conf.d/router/900_exim4-config_local_user, and change the LOCAL_DELIVERY macro in conf.d/main/01_exim4-config_listmacrosdefs to LOCAL_DELIVERY=cyrus_delivery.

  If you still want to deliver some messages to a mail spool then create conf.d/router/899_exim4-config_copy_to_mbox and put this in it, changing the local_parts as necessary: (esto nunca lo hice)

copy_to_mbox:
      debug_print = "R: copy_to_mbox for $local_part@$domain"
      driver = accept
      unseen
      local_parts = postmaster
      transport = mail_spool

  This will deliver postmaster mail to both cyrus and /var/mail/postmaster.  You can comment the unseen option to have it only deliver once to the mail_spool.  If you don't set check_local_user or the user option the spool files will be owned by mail.

3. Kill any NULs (ASCII 0x00) inside the message, if you don't want Cyrus to bounce such malformed crap. Calling "tr -d '\000'" as a filter might do the trick.

4. Sieve often needs to set -f option on /usr/sbin/sendmail when doing redirects. Exim allows only trusted_users to do this. It is recommended that you make sure "cyrus" is in the list of trusted_users in conf.d/main/02_exim4-config_options:

trusted_users = uucp:cyrus