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 
Hey, I thought I removed that lines. They don't do anything as SplitHostPort will give an error if no port is specified.

As for the port number, 587 is the standard port used by all major email providers for mail submission and specified in RFC 6409: http://tools.ietf.org/html/rfc6409

I will submit a PR to remove these lines as I found adding a default port a bit too much work to be included in this patch.