When sendmail is running, you can find it in process listings under the name sendmail, regardless of how you ran it (e.g., as mailq). This is proper at the majority of sites that run only a single daemon. Some sites, however, run multiple daemons. For example, on a firewall machine one daemon might be listening to the outside interface, and another might be listening only on the internal interface. A process listing would show both, but give no clue as to which is which:

root     14384  IW   Dec 18  1:30 sendmail: accepting connections
root     15567  IW   Dec 18  4:34 sendmail: accepting connections

In such situations it can be useful to be able to differentiate between the two listing items. The ProcessTitlePrefix option allows you to do just that:

O ProcessTitlePrefix=prefix                configuration file (V8.10 and later) 
-OProcessTitlePrefix=prefix                command line (V8.10 and later) 
define(`confPROCESS_TITLE_PREFIX',`prefix')    mc configuration (V8.10 and later) 

Here, prefix is of type string. If it is absent, the prefix becomes an empty string. If the entire option is absent, no prefix is used. The default for the mc configuration technique is to leave this option undefined.

If the previous example of two sendmail daemons had been started at boot time using an rc file with lines such as these:

/usr/sbin/sendmail -OProcessTitlePrefix=inside -C/etc/mail/inside.cf -bd
/usr/sbin/sendmail -OProcessTitlePrefix=outside -C/etc/mail/outside.cf -bd

the previous process listing might look like this:

root     14384  IW   Dec 18  1:30 sendmail: outside: accepting connections
root     15567  IW   Dec 18  4:34 sendmail: inside: accepting connections

Note that this difference is evident only in the process listing, and that the prefix set by this option is not reflected in log lines.

The ProcessTitlePrefix option is not safe. If specified from the command line, it can cause sendmail to relinquish its special privileges.