Dovecot discards mail in a certain situation

[Aleš Pečnik]

Hi all:

I'm using Dovecot with Postfix (via LMTP). Because Postfix doesn't 
de-duplicate recipients, I'm using sieve to drop duplicates, following 
this recipe: 
https://serverfault.com/questions/112958/postfix-aliases-and-duplicate-e-mails-how-to-fix

A "sieve_before" script contains:

require ["duplicate"];
if duplicate
{
   discard;
   stop;
}

It works well, except when the recipient is over quota. Dovecot is 
configured for tempfail in this case: quota_full_tempfail = yes

When a mail arrives for a user who's over quota, Postfix logs this:

AF4481700032: to=<?@?>, relay=?[private/dovecot-lmtp], delay=0.05, 
delays=0.05/0/0/0, dsn=4.2.2, status=deferred (host 
?[private/dovecot-lmtp] said: 452 4.2.2 <?@?> Quota exceeded (mailbox 
for user is full) (in reply to end of DATA command))

Approximately 10 minutes later, Postfix retries, and log shows:

dovecot: lmtp(?)<1742912><+EYHBXjidmBAmBoAcAY70w>: sieve: 
msgid=<489132c2-7b77-cd2f-ce60-439f6558ddcf@?>: marked message to be 
discarded if not explicitly delivered (discard action)
postfix/lmtp[1742691]: AF4481700032: to=<?@?>, 
relay=?[private/dovecot-lmtp], delay=431, delays=431/0/0/0, dsn=2.0.0, 
status=sent (250 2.0.0 <?@?> +EYHBXjidmBAmBoAcAY70w Saved)
postfix/qmgr[421343]: AF4481700032: removed

The message is then nowhere to be found: it's not delivered to mailbox, 
bounce isn't sent to the sender, mail is not in postfix queue. 
Apparently it's been discarded.


I'd say that at first LMTP delivery attempt, sieve records message as 
seen, even though it is eventually rejected (452 over quota). During 
second attempt sieve "recognizes" the message as seen before and 
discards it. (This is just my interpretation of what could be happening.)


Is this a bug or have I misconfigured something? My dovecot -n output is 
below.


Thanks for help,

Aleš Pečnik



# dovecot -n
# 2.3.7.2 (3c910f64b): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.5.7.2 ()
# OS: Linux 5.4.0-62-generic x86_64 Ubuntu 20.04.1 LTS
auth_mechanisms = plain login
auth_username_chars = 
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890.-_@:
auth_username_format = %Ln
auth_worker_max_count = 3
default_vsz_limit = 1 G
first_valid_gid = 12
first_valid_uid = 8
hostname = something.org
last_valid_gid = 12
last_valid_uid = 8
listen = *
mail_access_groups = mail
mail_location = maildir:/var/dovecot/%u
mail_plugins = " quota mailbox_alias mail_log notify acl"
mail_privileged_group = mail
namespace {
   location = maildir:/var/dovecot/public:INDEXPVT=/var/dovecot/%n/public
   prefix = Public.
   separator = .
   subscriptions = no
   type = public
}
namespace inbox {
   inbox = yes
   location =
   mailbox Drafts {
     auto = no
     special_use = \Drafts
   }
   mailbox Junk {
     special_use = \Junk
   }
   mailbox Sent {
     auto = subscribe
     special_use = \Sent
   }
   mailbox "Sent Messages" {
     auto = no
     special_use = \Sent
   }
   mailbox Trash {
     auto = no
     special_use = \Trash
   }
   prefix =
}
passdb {
   args = /etc/dovecot/dovecot-sql-master.conf.ext
   driver = sql
   master = yes
   pass = yes
}
passdb {
   args = /etc/dovecot/dovecot-sql.conf.ext
   driver = sql
}
plugin {
   acl = vfile
   mailbox_alias_new = Sent Messages
   mailbox_alias_new2 = Sent Items
   mailbox_alias_new3 = Deleted Items
   mailbox_alias_new4 = Deleted Messages
   mailbox_alias_old = Sent
   mailbox_alias_old2 = Sent
   mailbox_alias_old3 = Trash
   mailbox_alias_old4 = Trash
   quota = maildir:User quota
   quota_rule = *:storage=200M
   quota_rule2 = Trash:storage=+50M
   quota_warning = storage=95%% quota-warning 95 %u
   quota_warning2 = storage=80%% quota-warning 80 %u
   sieve = 
file:/var/dovecot/%n/sieve;active=/var/dovecot/%n/sieve/active.sieve
   sieve_before = /var/lib/dovecot/sieve.d/
   sieve_extensions = +notify +imapflags +editheader +duplicate
}
postmaster_address = postmaster at something.org
protocols = " imap lmtp"
quota_full_tempfail = yes
service auth {
   unix_listener /var/spool/postfix/private/auth {
     group = postfix
     mode = 0660
     user = postfix
   }
}
service imap-login {
   inet_listener imap {
     port = 143
   }
   inet_listener imaps {
     port = 0
   }
   process_min_avail = 12
   service_count = 0
}
service imap-postlogin {
   executable = script-login /etc/dovecot/postlogin.sh
   user = $default_internal_user
}
service imap {
   executable = imap imap-postlogin
}
service lmtp {
   unix_listener /var/spool/postfix/private/dovecot-lmtp {
     group = postfix
     mode = 0600
     user = postfix
   }
}
service pop3-login {
   inet_listener pop3 {
     port = 0
   }
   inet_listener pop3s {
     port = 0
   }
}
ssl_cert = </etc/ssl/my.crt
ssl_client_ca_dir = /etc/ssl/certs
ssl_dh = # hidden, use -P to show it
ssl_key = # hidden, use -P to show it
userdb {
   args = /etc/dovecot/dovecot-sql.conf.ext
   driver = sql
}
protocol lmtp {
   mail_plugins = " quota mailbox_alias mail_log notify acl sieve"
}
protocol lda {
   mail_plugins = " quota mailbox_alias mail_log notify acl sieve"
}
protocol imap {
   mail_max_userip_connections = 30
   mail_plugins = " quota mailbox_alias mail_log notify acl imap_quota 
imap_acl"
}

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