In reply to a post by XRaySpeX:

Agreed, but then you would expect some response when you do type something even if erroneous. At least with the TBB one you do get some feedback when you type into it.

It is normal for a server expecting an SSL handshake to simply terminate the connection without returning any data to the client if data is received from the client that is not an SSL handshake, because protocol dictates that no data should be sent unencrypted over these connections.

On the other hand, since port 80 is not an encrypted port and is not expecting an SSL handshake, it will happily send some unencrypted data to the client before terminating the connection.

BatBoy is correct.
Try using PuTTy and tell it to use RAW as the connection type, telnet sends control characters before each line, including when it connects etc.

Now enter something then press return, it will then disconnect you, so you will see you can connect to that address on that port number.

If you was unable to connect to a specific address it would just sit there until it times out, or in some cases the server closes connection, whereas this is terminating the connection right away, but is due to sending telnet codes and the server say nope that's not SSL/TLS (Transport Layer Security) packets and closes the connection.

If its a port number setup for SSL (think it may use TLS) then you won't see anything due to its expecting an encrypted packet.
SMTP is different, your mail app checks to see what it supports and uses one of those, so you see a welcome message from that.

Paul