FreeBSD Tip: Fixing a Sendmail Error After Removing IPv6

When I'm rebuilding my kernel in FreeBSD I comment out the INET6 option.#options INET6 # IPv6 communications protocolsI don't run anything using the IPv6 protocol so I feel it's a waste of time having it there. However this causes an error in sendmail, that you will see in your /var/log/messages file, and your root mail for example:Oct 16 01:45:12 MyKernalName sendmail[5216]: NOQUEUE: SYSERR(root): /etc/mail/sendmail.cf: line 279: Unknown address family inet6 in Family=optionand in your /var/log/debug.log file you will often see:Oct 16 01:45:12 MyKernalName kernel: drop session, too many entries
There is a really easy solution to this problem, first open the sendmail.cf file for editing, (I'm using vi, but you can use your preferred editor for this operation):# vi /etc/mail/sendmail.cfNow navigate to line #No 279 and comment it out, to look like this:#O DaemonPortOptions=Name=IPv6, Family=inet6, Modifiers=OOnce you have saved your file you'll need to reboot or restart the sendmail process so that it re-reads its config file, and your problem will be solved.