How to ping email server with port number.

Ping will tell you if you can connect to the server, but doesn't tell you anything about Port 25. The 'ping' command generates an ICMP echo request packet. ICMP is a protocol over IP that implements "control messages" (flow control, routing, etc.). At that level the very concept of TCP/UDP ports is completely irrelevant.
Start off with "PING \\MyServerName" or "Ping 10.10.10.1" or whatever if you know the IP Address of the mail server.That will tell you whether you can see the Server or not.If you get a valid response to the Ping, try telnetting into the Server with "TELNET \\MyServerName 25" or "TELNET \\10.10.10.1" or whatever. You will either get a welcome message form the SMTP Server or see a "Connecting...." message which will time out. If you get a valid response from the SMTP Server, just type QUIT and hit enter to get out again (note you will probably not see your keystrokes echoed to your screen, so make sure you type it corrrectly)