How do I install stunnel on Yosemite server 4 so my mail relay works on port 465?

Question

My ISP blocks outbound smtp mail and insists I point to their relay server on port 465.  After I set up mail relaying in the server config app I get SMTP log errors saying it's unimplemented.  After some research it looks like I need to install a SSL tunnel package called stunnel.  Has anyone had an success getting stunnel installed?  Or, has anyone had any luck using Yosemite Server 4 to mail relay through verizon.net (port 465)?  Any suggestions are much appreciated.

Answer 1

I'll assume that you have to authenticate to the mail relay with a name and password. The Server GUI doesn't provide for this use case.
Take the following steps to configure Postfix to relay mail to a remote SMTP server with password authentication over SSL. Substitute as required for strings in italics below. Address is the fully-qualified domain name of the relay host. The value of port is usually either 25, 465, or 587. Username and password refer to your credentials on the relay host.
In the current version of OS X Server (but not necessarily in older versions), Steps 1 and 3 should be done for you when you enable relaying and relay authentication in the Server application.
1. If necessary, create or update the relayhost directive in
     /Library/Server/Mail/Config/postfix/main.cf
It should look like this:
     relayhost = [address]:port
2. Add these lines, above the section at the end that begins with the comment "# Mac OS X Server":
     smtp_sasl_security_options =
     smtp_tls_CAfile = /etc/certificates/relayhost.pem
     smtp_tls_session_cache_database = btree:$data_directory/smtp_tls_session_cache
     smtp_use_tls = yes
3. If it doesn't already exist, create the password file
     /Library/Server/Mail/Config/postfix/sasl/passwd
with this content:
     [address]:port
     username:password
Here address must match $relayhost.
Then create the password database:
sudo postmap /Library/Server/Mail/Config/postfix/sasl/passwd
This action creates the file
     /Library/Server/Mail/Config/postfix/sasl/passwd.db
The two password files should be readable by root only.
4. Create the file
     /etc/certificates/relayhost.pem
with the CA certificate(s) to be trusted for authentication of the remote host. You get those certificates from the service provider. If you can't find a link to download them, try this:
openssl s_client -connect address:port -showcerts < /dev/null | sed -n '/-BEGIN /,/-END /p' | sudo sh -c 'cat > /etc/certificates/relayhost.pem'
The command may produce an error message that isn't necessarily significant. For servers that use the older STARTTLS protocol, rather than straight TLS or SSL, this command may need to be modified.
5. Restart the Mail service.