To extend my previous message : I added the option '-o lmtp_destination_recipient_limit=1' to Postfix and try again to send a message to someone outside my domains, but adding two people in CC. It seems that Dovecot is still handling the delivery incorrectly. Here is the transcript of what happened :
May 26 09:39:00 lmtp(47593): Debug: none: root=, index=, indexpvt=, control=, inbox=, alt= May 26 09:39:00 lmtp(47593): Info: Connect from 9.6.71.10 May 26 09:39:00 lmtp(47593): Debug: Loading modules from directory: /usr/local/lib/dovecot May 26 09:39:00 lmtp(47593): Debug: Module loaded: /usr/local/lib/dovecot/lib10_mailden_filter_plugin.so May 26 09:39:00 lmtp(47593): Debug: auth input: cont...@mailden.pro home=/mailboxes/mailden.pro/contact/ uid=200 gid=6 email=cont...@mailden.pro May 26 09:39:00 lmtp(47593): Debug: Added userdb setting: plugin/email=cont...@mailden.pro May 26 09:39:00 lmtp(47593): Debug: auth input: s...@sapienssapide.fr home=/mailboxes/sapienssapide.fr/stan/ uid=200 gid=6 email=s...@sapienssapide.fr May 26 09:39:00 lmtp(47593): Debug: Added userdb setting: plugin/email=s...@sapienssapide.fr May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Info: mailden_filter_plugin_init May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Debug: Effective uid=200, gid=6, home=/mailboxes/mailden.pro/contact/ May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Info: mailden_filter_mail_user_created May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Info: mailden_filter_parse_setting May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Debug: mailden_filter: Filtering mailden_filter via socket /var/run/dovecot//decrypt-filter May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Info: mailden_filter_parse_setting May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Debug: mailden_filter: Filtering mailden_filter_out via socket /var/run/dovecot//encrypt-filter May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Info: plain_pass is null May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Debug: Namespace inbox: type=private, prefix=, sep=, inbox=yes, hidden=no, list=yes, subscriptions=yes location=dbox:/mailboxes/mailden.pro/contact/ May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Debug: fs: root=/mailboxes/mailden.pro/contact, index=, indexpvt=, control=, inbox=, alt= May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Info: mailden_filter_mailbox_allocated May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Info: mailden_filter_mail_allocated May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Info: mailden_filter_mail_save_begin May 26 09:39:00 box encrypt_mail: -> Encrypt arg : cont...@mailden.pro May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Debug: Namespace : Using permissions from /mailboxes/mailden.pro/contact: mode=0700 gid=default May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Info: sjhnApTvglPpuQAAz9GZsw: msgid=<5382efa2.7020...@mailden.fr>: saved mail to INBOX May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Info: mailden_filter_mail_allocated May 26 09:39:00 lmtp(47593, cont...@mailden.pro): Info: mailden_filter_istream_opened May 26 09:39:00 lmtp(47593, s...@sapienssapide.fr): Debug: Effective uid=200, gid=6, home=/mailboxes/sapienssapide.fr/stan/ May 26 09:39:00 lmtp(47593, s...@sapienssapide.fr): Info: mailden_filter_mail_user_created May 26 09:39:00 lmtp(47593, s...@sapienssapide.fr): Info: mailden_filter_parse_setting May 26 09:39:00 lmtp(47593, s...@sapienssapide.fr): Debug: mailden_filter: Filtering mailden_filter via socket /var/run/dovecot//decrypt-filter May 26 09:39:00 lmtp(47593, s...@sapienssapide.fr): Info: mailden_filter_parse_setting May 26 09:39:00 lmtp(47593, s...@sapienssapide.fr): Debug: mailden_filter: Filtering mailden_filter_out via socket /var/run/dovecot//encrypt-filter May 26 09:39:00 lmtp(47593, s...@sapienssapide.fr): Info: plain_pass is null May 26 09:39:00 lmtp(47593, s...@sapienssapide.fr): Debug: Namespace inbox: type=private, prefix=, sep=, inbox=yes, hidden=no, list=yes, subscriptions=yes location=dbox:/mailboxes/sapienssapide.fr/stan/ May 26 09:39:00 lmtp(47593, s...@sapienssapide.fr): Debug: fs: root=/mailboxes/sapienssapide.fr/stan, index=, indexpvt=, control=, inbox=, alt= May 26 09:39:00 lmtp(47593, s...@sapienssapide.fr): Info: mailden_filter_mailbox_allocated May 26 09:39:00 lmtp(47593, s...@sapienssapide.fr): Info: mailden_filter_mail_allocated May 26 09:39:00 lmtp(47593, s...@sapienssapide.fr): Debug: Namespace : Using permissions from /mailboxes/sapienssapide.fr/stan: mode=0700 gid=default May 26 09:39:00 lmtp(47593, s...@sapienssapide.fr): Info: sjhnApTvglPpuQAAz9GZsw: msgid=<5382efa2.7020...@mailden.fr>: saved mail to INBOX May 26 09:39:00 lmtp(47593): Info: Disconnect from 9.6.71.10: Successful quit May 26 09:39:00 box decrypt_mail: -> Decrypt arg : cont...@mailden.pro,n The last line above shows that, again, Dovecot is trying to read the email from mailboxe and it launched the 'decypt_mail' program with user1's params (user1 = 'cont...@mailden.pro'). At this stage, neither user1 (cont...@mailden.pro) nor user2 (s...@sapienssapide.fr) are connected and authenticated. Therefore, decrypt_mail is launched without user1's password (decrypc args are email and user password. In the above case, user password is set to 'n' because is missing). Stan.