#!/bin/bash # # Dovecot (IMAP/POP and LDA) # ---------------------- # # Dovecot is *both* the IMAP/POP server (the protocol that email applications # use to query a mailbox) as well as the local delivery agent (LDA), # meaning it is responsible for writing emails to mailbox storage on disk. # You could imagine why these things would be bundled together. # # As part of local mail delivery, Dovecot executes actions on incoming # mail as defined in a "sieve" script. # # Dovecot's LDA role comes after spam filtering. Postfix hands mail off # to Spamassassin which in turn hands it off to Dovecot. This all happens # using the LMTP protocol. source setup/functions.sh # load our functions source /etc/mailinabox.conf # load global vars # Install packages... apt_install \ dovecot-core dovecot-imapd dovecot-pop3d dovecot-lmtpd dovecot-sqlite sqlite3 \ dovecot-sieve dovecot-managesieved # The `dovecot-imapd`, `dovecot-pop3d`, and `dovecot-lmtpd` packages automatically # enable IMAP, POP and LMTP protocols. # Set basic daemon options. # The `default_process_limit` is 100, which constrains the total number # of active IMAP connections (at, say, 5 open connections per user that # would be 20 users). Set it to 250 times the number of cores this # machine has, so on a two-core machine that's 500 processes/100 users). tools/editconf.py /etc/dovecot/conf.d/10-master.conf \ default_process_limit=$(echo "`nproc` * 250" | bc) # The inotify `max_user_instances` default is 128, which constrains # the total number of watched (IMAP IDLE push) folders by open connections. # See http://www.dovecot.org/pipermail/dovecot/2013-March/088834.html. # A reboot is required for this to take effect (which we don't do as # as a part of setup). Test with `cat /proc/sys/fs/inotify/max_user_instances`. tools/editconf.py /etc/sysctl.conf \ fs.inotify.max_user_instances=1024 # Set the location where we'll store user mailboxes. '%d' is the domain name and '%n' is the # username part of the user's email address. We'll ensure that no bad domains or email addresses # are created within the management daemon. tools/editconf.py /etc/dovecot/conf.d/10-mail.conf \ mail_location=maildir:$STORAGE_ROOT/mail/mailboxes/%d/%n \ mail_privileged_group=mail \ first_valid_uid=0 # ### IMAP/POP # Require that passwords are sent over SSL only, and allow the usual IMAP authentication mechanisms. # The LOGIN mechanism is supposedly for Microsoft products like Outlook to do SMTP login (I guess # since we're using Dovecot to handle SMTP authentication?). tools/editconf.py /etc/dovecot/conf.d/10-auth.conf \ disable_plaintext_auth=yes \ "auth_mechanisms=plain login" # Enable SSL, specify the location of the SSL certificate and private key files. # Disable obsolete SSL protocols and allow only good ciphers per http://baldric.net/2013/12/07/tls-ciphers-in-postfix-and-dovecot/. tools/editconf.py /etc/dovecot/conf.d/10-ssl.conf \ ssl=required \ "ssl_cert=<$STORAGE_ROOT/ssl/ssl_certificate.pem" \ "ssl_key=<$STORAGE_ROOT/ssl/ssl_private_key.pem" \ "ssl_protocols=!SSLv3 !SSLv2" \ "ssl_cipher_list=TLSv1+HIGH !SSLv2 !RC4 !aNULL !eNULL !3DES @STRENGTH" # Disable in-the-clear IMAP/POP because there is no reason for a user to transmit # login credentials outside of an encrypted connection. Only the over-TLS versions # are made available (IMAPS on port 993; POP3S on port 995). sed -i "s/#port = 143/port = 0/" /etc/dovecot/conf.d/10-master.conf sed -i "s/#port = 110/port = 0/" /etc/dovecot/conf.d/10-master.conf # Make IMAP IDLE slightly more efficient. By default, Dovecot says "still here" # every two minutes. With K-9 mail, the bandwidth and battery usage due to # this are minimal. But for good measure, let's go to 4 minutes to halve the # bandwidth and number of times the device's networking might be woken up. # The risk is that if the connection is silent for too long it might be reset # by a peer. See #129 and http://razor.occams.info/blog/2014/08/09/how-bad-is-imap-idle/. tools/editconf.py /etc/dovecot/conf.d/20-imap.conf \ imap_idle_notify_interval="4 mins" # Set POP3 UIDL # UIDLs are used by POP3 clients to keep track of what messages they've downloaded. # For new POP3 servers, the easiest way to set up UIDLs is to use IMAP's UIDVALIDITY # and UID values, the default in Dovecot. tools/editconf.py /etc/dovecot/conf.d/20-pop3.conf \ pop3_uidl_format = %08Xu%08Xv # ### LDA (LMTP) # Enable Dovecot's LDA service with the LMTP protocol. It will listen # on port 10026, and Spamassassin will be configured to pass mail there. # # The disabled unix socket listener is normally how Postfix and Dovecot # would communicate (see the Postfix setup script for the corresponding # setting also commented out). # # Also increase the number of allowed IMAP connections per mailbox because # we all have so many devices lately. cat > /etc/dovecot/conf.d/99-local.conf << EOF; service lmtp { #unix_listener /var/spool/postfix/private/dovecot-lmtp { # user = postfix # group = postfix #} inet_listener lmtp { address = 127.0.0.1 port = 10026 } } protocol imap { mail_max_userip_connections = 20 } EOF # Setting a `postmaster_address` is required or LMTP won't start. An alias # will be created automatically by our management daemon. tools/editconf.py /etc/dovecot/conf.d/15-lda.conf \ postmaster_address=postmaster@$PRIMARY_HOSTNAME # ### Sieve # Enable the Dovecot sieve plugin which let's users run scripts that process # mail as it comes in. sed -i "s/#mail_plugins = .*/mail_plugins = \$mail_plugins sieve/" /etc/dovecot/conf.d/20-lmtp.conf # Configure sieve. We'll create a global script that moves mail marked # as spam by Spamassassin into the user's Spam folder. # # * `sieve_before`: The path to our global sieve which handles moving spam to the Spam folder. # # * `sieve`: The path to the user's main active script. ManageSieve will create a symbolic # link here to the actual sieve script. It should not be in the mailbox directory # (because then it might appear as a folder) and it should not be in the sieve_dir # (because then I suppose it might appear to the user as one of their scripts). # * `sieve_dir`: Directory for :personal include scripts for the include extension. This # is also where the ManageSieve service stores the user's scripts. cat > /etc/dovecot/conf.d/99-local-sieve.conf << EOF; plugin { sieve_before = /etc/dovecot/sieve-spam.sieve sieve = $STORAGE_ROOT/mail/sieve/%d/%n.sieve sieve_dir = $STORAGE_ROOT/mail/sieve/%d/%n } EOF # Copy the global sieve script into where we've told Dovecot to look for it. Then # compile it. Global scripts must be compiled now because Dovecot won't have # permission later. cp conf/sieve-spam.txt /etc/dovecot/sieve-spam.sieve sievec /etc/dovecot/sieve-spam.sieve # PERMISSIONS # Ensure configuration files are owned by dovecot and not world readable. chown -R mail:dovecot /etc/dovecot chmod -R o-rwx /etc/dovecot # Ensure mailbox files have a directory that exists and are owned by the mail user. mkdir -p $STORAGE_ROOT/mail/mailboxes chown -R mail.mail $STORAGE_ROOT/mail/mailboxes # Same for the sieve scripts. mkdir -p $STORAGE_ROOT/mail/sieve chown -R mail.mail $STORAGE_ROOT/mail/sieve # Allow the IMAP/POP ports in the firewall. ufw_allow imaps ufw_allow pop3s # Restart services. restart_service dovecot