Rewrite of SendMail function

The SendMail function is rewritten and has the following new functionality:
 - It is optional to skip verification of keys. The config option SKIP_VERIFY is added
 - If the port is 465, or ending on 465, the TLS(/SSL) connection is started first.

Should resolve #749 
Oops, not instead but plus.
I want to say that code should realize next idea: if no password was specified then no auth shouldn't be started