If you allow incoming mail over an IPC connection, you should
have a daemon running. This should be set by your /etc/mail/sendmailrc file
using the -bd flag. The -bd flag and the -q
flag may be combined in one call:
/usr/lib/sendmail -bd -q30m
An alternative approach is to invoke sendmail from
inetd(1Mtcp)
(use the -bs flag to ask sendmail to speak SMTP on
its standard input and output). This works and allows you to wrap
sendmail(1M)
in a TCP wrapper program, but may be a bit slower since the
configuration file has to be re-read on every message that comes in.
If you do this, you still need to have a
sendmail running to flush the queue:
/usr/lib/sendmail -q30m