If you installed any or all of the ClamAV and ClamSMTP components via a package manager rather than from source, the necessary startup scripts may have been provided. Check to see if the necessary scripts have been included in the boot startup sequence.
If you have installed ClamAV from the source code, the following scripts are examples for starting and stopping the necessary daemons at boot time. Depending on your distribution, the file locations may vary and you may need to execute additional commands to set run levels for each script. Please consult your distributions documentation.
One of the contributed scripts that are available in the ClamSMTP sources is a script to be used for automatically starting and stopping the operating daemon when the system is booted. Check that the path names in the script match those in the config file and the installed directory, and then execute the following command from the root of the ClamSMTP source tree...