Sendmail DSN Error - OLD TITLE(Sendmail Smart Host using TLS - host is rejecting)

Question

I am trying to set up a new installation of Sendmail on my FreeBSD server with a dual-MTA SA/VS implementation. Everything seems to work well when I handle the mail on my own, but when I try to send the mail through my smart host (which I do on my other server without issue) I get a Service Not Available message from the host. It appears as though my sendmail is trying to send mail to my smart host using TLS and as such is getting rejected by the smart host.

This is the line in my sendmail.cf file which defines my smart host:

define(`SMART_HOST', `smtp.comcast.net')dnl

here is my log output when trying to send a message:

Jan 9 20:36:51 shep sendmail[4814]: STARTTLS=client, relay=smtp.comcast.net, version=TLSv1/SSLv3, verify=FAIL, cipher=DHE-RSA-AES256-SHA, bits=256/256
Jan 9 20:36:51 shep sendmail[4814]: r0A1apXE004812: to=myemail@gmail.com, ctladdr=root (0/0), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30038, relay=smtp.comcast.net [68.87.26.155], dsn=5.0.0, stat=Service unavailable

I would like it to just send it to the smart host without the cipher crap, how do I disable it?

This is a log entry from my other server where it works properly with the smart host:

Jan 9 21:48:09 karma sm-mta[89472]: r0A2m2d8089469: to=, ctladdr= (1001/0), delay=00:00:02, xdelay=00:00:01, mailer=relay, pri=30351, relay=smtp.comcast.net [68.87.26.155], dsn=2.0.0, stat=Sent (m2tP1k00o3Nw2a03Y2tQjg mail accepted for delivery)

Thanks,

Lou

Answer 1

So I was just going to erase this post since the title is misleading. I have solved the issue and I've decided to keep the question and answer because it seems to have been a problem for others, so I hope it helps out.

The true problem being observed above is a DSN Error, NOT DNS, but DSN. A sendmail DSN or Delivery Status Notification is a function that is part of the sendmail MTA.

What happened is that when I sent mail from my command line I got the DSN error because the hostname was not set in my sendmail.cf file.

I noticed this when I sent mail from another mail client and it went through OK, then I looked further into the sendmail DSN itself.

Adding the following line to my mc file then recompiling it into its corresponding cf file fixed the problem:

define(`confDOMAIN_NAME', `your.domainnamehere.com')dnl

Answer 2

Solved my sendmail issued.

I put the following into sendmail.mc

define(`confDOMAIN_NAME', `smtp.gmail.com')dnl

define(`SMART_HOST', `smtp.gmail.com')dnl

define(`confAUTH_MECHANISMS`, `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN`)dnl

FEATURE('authinfo','hash /etc/mail/auth/client-info')dnl