; cat /bin/service/tcp25
#!/bin/rc
#smtp serv net incalldir user

user=`{cat /dev/user}
exec upas/smtpd -e -f -r -s -n 3

exec upas/smtpd -c /sys/lib/tls/acmed/example.com.crt -e -f -r -s -n 3

#
#	sample smtpd configuration options for inside connections
#

#
#	replace example.com with the name of your domain
#	replace 198.51.100.0 with the IP address range of your networks

defaultdomain		example.com
norelay			on	
verifysenderdom		off	#disable dns verification of sender domain
saveblockedmsg		off	#save blocked messages

#
# if norelay is on, you need to set the
# networks allowed to relay through 
# as well as the domains to accept mail for
#

ournets 198.51.100.0/24

ourdomains *.example.com

Copy /mail/lib/rewrite.direct to /mail/lib/rewrite, while replacing YOURDOMAIN.DOM with your actual domain name.

You will also want to edit /mail/lib/names.local for the users you want to handle mail for.

Edit /mail/lib/remotemail to add the -C -s flags to turn on TLS encryption when sending.
-C is needed in case some certificates don't validate properly:

#!/bin/rc
shift
sender=1
shift
addr=1
shift
fd=`{/bin/upas/aliasmail -f sender}
switch(fd){
case *.*
	;
case *
	fd=example.com
}
exec /bin/upas/smtp -C -s -h fd addr sender *

Make sure to replace example.com with your actual domain name.

If you are logged in as a user other than the default hostowner (glenda),
make sure to add the users to upas group:

; echo 'newuser upas +username' >> /srv/cwfs.cmd

Then create the user's mailbox:

; upas/nedmail -c

; upasname=sender@example.com upas/marshal -s 'Alpha Bravo Charlie' recipient@example.org