To run Exim, you must first decide whether you want it to handle incoming SMTP
messages by running as a separate daemon, or whether to have
inetd manage the SMTP port and invoke Exim only whenever an
SMTP connection is requested from a client. Usually, you will prefer daemon
operation on the mail server because it loads the machine far less than
spawning Exim over and over again for each connection. As the mail server also
delivers most incoming mail directly to the users, you should choose
inetd operation on most other hosts.
Whatever mode of operation you choose for each individual host, you
have to make sure you have the following entry in your
smtp 25/tcp # Simple Mail Transfer Protocol
This defines the TCP port number that is used for SMTP conversations.
Port number 25 is the standard defined by the “Assigned Numbers”
When run in daemon mode, Exim puts itself in the background and waits for
connections on the SMTP port. When a connection occurs, it forks, and the
child process conducts an SMTP conversation with the peer process on the
calling host. The Exim daemon is usually started by invoking it from the
rc script at boot time using the following command:
The –bd flag turns on daemon mode, and
–q15m makes it process whatever messages have
accumulated in the message queue every 15 minutes.
If you want to use inetd instead, your
/etc/inetd.conf file should contain a line like this:
smtp stream tcp nowait root /usr/sbin/exim in.exim -bs
Remember you have to make inetd re-read
inetd.conf by sending it an
HUP signal after
making any changes.
Daemon and inetd modes are mutually exclusive. If
you run Exim in daemon mode, you should make sure to comment out any line in
inetd.conf for the
smtp service. Equivalently, when
having inetd manage Exim, make sure that no
rc script starts the Exim daemon.
You can check that Exim is correctly set up for receiving incoming SMTP
messages by telnetting to the SMTP port on your machine. This is what a
successful connect to the SMTP server looks like:
$ telnet localhost smtp
Connected to localhost.
Escape character is '^]'.
220 richard.vbrew.com ESMTP Exim 3.13 #1 Sun, 30 Jan 2000 16:23:55 +0600
221 richard.brew.com closing connection
Connection closed by foreign host.
If this test doesn't produce the SMTP banner (the line starting with the
220 code), check that you are either running an Exim daemon process or
have inetd correctly configured. If that doesn't reveal
the problem, look in the Exim log files (described next) in case
there is an error in Exim's configuration file.