Problems in verifying connection to CF Administrator Mail Server

I  need to send e-mails using CFMAIL, but am unable to verify the connection to the CF Administrator Mail Server, which presently is localhost.

This question has been asked in other places, but I have checked the remedies suggested there (firewall blocking, etc) to no avail.

I am using Server Port 25 and have tried enabling both TLS and SSL.

There are no basic Server issues, since I get the message "Server has been updated successfully" upon re-entering the Server Settings data.

Thanks in advance for comments.