/etc/make.conf

I'd suggest copying the host environment's /etc/make.conf into the jail, since most of the settings will still apply. Two useful additions are:

SENDMAIL_MC=/etc/mail/jailenvironment.domain.com.mc
WRKDIRPREFIX=/var/tmp

The first line is in accordance with LocalSendmailConfiguration practices. When the jail's admin runs make install in /etc/mail, the Makefile will look for a file by that name. If one doesn't exist, then it copies /etc/mail/freebsd.mc to a new file with that name, then runs uses that file to build the configuration. However, at some time or another (probably right after following the instructions in BuildAndUpdateJails), you'll ChRoot^? to this jail's filesystem to do a bit of maintenance. If you happen to run make install then, the Makefile will see a different system hostname than if you were running it from inside the jail, and will look for /etc/mail/hostenvironment.domain.com.mc. Since it doesn't exist, it will use freebsd.mc (the default file) to generate sendmail.cf, and will completely ignore any local customizations. Just hardcode this value and forget about it - it'll pay off later.

The second line tells the PortsCollection to build programs under /var/tmp instead of under /usr/ports. This is handy if you mount /usr/ports as a read-only filesystem inside the jail, i.e. if you want to use NFS to replicate /usr/ports to many separate JailEnvironments without wasting n copies of that drive space.

/etc/rc.conf

LocalSendmailConfiguration:

Note that I do not receive mail in any of my jails. If you're running a hosting provider, you'll need to adjust these settings accordingly.

/etc/rc.conf:

# Use a secure connection to administer the jail
sshd_enable="YES"

inetd_enable="YES"
nisdomainname="NO"

# Run syslogd locally
syslogd_enable="YES"
syslogd_flags="-a 127.0.0.1/8"

# Turn on connection logging
inetd_flags="-wWl"

# Only allow outgoing email
sendmail_enable="NONE"
sendmail_submit_enable="NO"
sendmail_outbound_enable="YES"  # Dequeue stuck mail (YES/NO).
sendmail_outbound_flags="-L sm-queue -q30m" # Flags to sendmail (outbound only)
sendmail_msp_queue_enable="YES" # Dequeue stuck clientmqueue mail (YES/NO).
sendmail_msp_queue_flags="-L sm-msp-queue -Ac -q30m"
                                # Flags for sendmail_msp_queue daemon.
# Not appropriate for jails
tcp_keepalive="NO"
tcp_extensions="NO"

LocalSendmailConfiguration:

-dnl define(`SMART_HOST', `your.isp.mail.server')
+define(`SMART_HOST', `hostenvironment.domain.com')

-- KirkStrauser - 11 Dec 2002