I was just installing a new sendmail server and once again stumbled across the default solaris config that will only bind this service to localhost. I knew this could be fixed somewhere in the svc properties but since this is not my daily cup of tea, I had to google this and it took me a few minutes. Anyway, this is what I came up with:
svccfg -v -s sendmail setprop config/local_only=false
svcadm refresh sendmail
svcadm restart sendmail
I found it at this blog.