pop3d - Cyrus IMAP documentation

       The Cyrus Team, Nic Bernstein (Onlight)

       1993–2025, The Cyrus Team

3.10.2                                            Jun 27, 2025                                          POP3D(8)

pop3d  is an POP3 server.  It accepts commands on its standard input and responds on its standard output.
       It MUST be invoked by master(8) with those descriptors attached to a remote client connection.

       pop3d reads its configuration options out of the imapd.conf(5) file unless specified otherwise by -C.

       If the directory log/user exists under the  directory  specified  in  the  configdirectory  configuration
       option, then pop3d will create protocol telemetry logs for sessions authenticating as user.

       The telemetry logs will be stored in the log/user directory with a filename of the pop3d process-id.

pop3d is commonly included in the SERVICES section of cyrus.conf(5) like so:

          SERVICES {
              imap        cmd="imapd -U 30" listen="imap" prefork=0
              imaps       cmd="imapd -s -U 30" listen="imaps" prefork=0 maxchild=100
              pop3cmd="pop3d-U30"listen="pop3"prefork=0pop3scmd="pop3d-s-U30"listen="pop3s"prefork=0maxchild=100
              lmtpunix    cmd="lmtpd" listen="/var/run/cyrus/socket/lmtp" prefork=0 maxchild=20
              sieve       cmd="timsieved" listen="sieve" prefork=0
              notify      cmd="notifyd" listen="/var/run/cyrus/socket/notify" proto="udp" prefork=1
              httpd       cmd="httpd" listen=8080 prefork=1 maxchild=20
          }

       /etc/imapd.conf

       pop3d - Cyrus IMAP documentation

       POP3 server process

-Cconfig-file
              Use the specified configuration file config-file rather than the default imapd.conf(5).

       -Uuses
              The  maximum  number  of times that the process should be used for new connections before shutting
              down.  The default is 250.

       -Ttimeout
              The number of seconds that the process will wait for a new connection before shutting down.   Note
              that a value of 0 (zero) will disable the timeout.  The default is 60.

       -D     Run external debugger specified in debug_command.

       -s     Serve  POP3  over  SSL  (pop3s).  All data to and from pop3d is encrypted using the Secure Sockets
              Layer.

       -k     Serve MIT's KPOP (Kerberized POP) protocol instead.

       -pssf Tell pop3d that an external layer exists.  An  SSF  (security  strength  factor)  of  1  means  an
              integrity protection layer exists.  Any higher SSF implies some form of privacy protection.

imapd.conf(5), master(8)

pop3d [ -Cconfig-file ] [ -Uuses ] [ -Ttimeout ] [ -D ]
              [ -s ] [ -k ] [ -pssf ]