Dovecot Sieve and Postfix header_checks Issue

[Klaipedaville on Google]

Hello List,

I tried to subscribe but it's taking forever for the confirmation email to arrive so I thought I would ask away by emailing directly. My apologies in advance should this question appear twice.

It may seem real simple to experts but I cannot really figure it out. I'll try to be concise:

Dovecot version is 2.1.7. Its dovecot –n is real short one and follows right after my question.

I have my Postfix 2.9.6 properties set like this: header_checks = /etc/path/to/myfile. Then I have Dovecot Sieve also configured and working fine.

Now the trouble is that these two cannot be combined together can they? Dovecot Sieve and Postfix's header_checks?  If I turn off header_checks in Postfix then Dovecot Sieve is working fine. If I vise versa turn off Dovecot Sieve then Postfix's header-checks are also working fine. However, when I keep them both turned on it also works but only partially and in this case Dovecot Sieve never bounces back any rejected massages remotely, the bounce happens only locally. That is I can see it in my logs that it was rejected locally but the message is never sent back to the sender saying something like, "Spam is rejected here". Thus the reject turns into a silent discard without telling the sender anything at all. Any ideas, help, advices how do I fix that? Would be really grateful for any suggestions / assistance at all. Many thanks in advance!

P.S. I would like to use both because Dovecot Sieve is a very powerful and great plugin that uses Spamassassin's added tags and headers based on which I create my rules. Postfix in its turn has a very neat feature of checking the headers via regexp but Postfix does not see / detect Spamassassin's added headers at all because I passed delivery and authentication (which is a way better than Postfix's) to dovecot deliver. 

# 2.1.7: /etc/dovecot/dovecot.conf
# OS: Linux 3.2.0-4-amd64 x86_64 Debian 7.6 ext4
auth_mechanisms = plain login cram-md5 scram-sha-1
auth_verbose = yes
hostname = WindTalker
info_log_path = /var/log/dovecot-sieve.log
log_path = /var/log/dovecot-sieve-errors.log
mail_location = maildir:/home/mvail/%d/%n
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date ihave
passdb {
  args = /etc/dovecot/passwd
  driver = passwd-file
}
plugin {
  sieve = ~/.dovecot.sieve
  sieve_default = /etc/dovecot/default.sieve
  sieve_dir = ~/sieve
}
pop3_uidl_format = %g
postmaster_address = postmaster at example.com
protocols = imap pop3 sieve
service auth {
  unix_listener /var/spool/postfix/private/auth {
    group = postfix
    mode = 0660
    user = postfix
  }
}
ssl_ca = </etc/ssl/ca.crt
ssl_cert = </etc/ssl//new.crt
ssl_key = </etc/ssl/new.key
userdb {
  args = uid=vmail gid=vmail home=/home/vmail/%u
  driver = static
}
protocol lda {
  mail_debug = yes
  mail_plugins = sieve
}

Regards,
Dennis.