This is actually an “old” tip. I write it here because I have been seeing some people are still using Options | Send menu to send message (SMS, MMS, Email). You can actually just press Call key to send message (no need to select Options | Send menu).

Sending text message in S60 phone Using Call key in S60 phone to send message

Compatible devices: S60 1st, 2nd, 3rd Edition, Nokia Nseries Nokia Eseries.