Test for a SMTP server :

While trobleshooting any email issues, This will help you to check your mail server with SMTP. To check this for your mail server, you can use telnet command to port 25 as:

# telnet 198.168.10.10 25
HELO test.test.com
MAIL FROM: from_email@domain.com
RCPT TO: to_email@domain.com
DATA
This is a test mail .Checking !!!!!
QUIT

198.168.10.10 is mail server ip.
You can use your hostname instead of Ip if the system you are on has the correct Domain Name Service (DNS) settings and can resolve the hostname of the mail server.

Please replace from_email@domain.com and to_email@domain.com with email addresses that you want to test.