Telnet to your smtp server using the following:
"telnet example.com 25". The number "25" is the default portnumber for outging mail, defined by IANA.
Substitute the address with your own address or ip number.
Even though this might very well be possible to do on your ISP mail server, dont!!
This will give you the SMTP server banner. I hope this has been changed or spoofed to protect from banner grabbing.
In my example, it gives me "220 example.com...