Sends mail to another user.
{"msg":"Mail","action":"Compose","to":"foo2","Subject":"example subject","Message":"hello world!","InviteCode":"my_session_id_here"}

The mail will be sent to the attented recipent:
{"MSG":"MailSent","To":"foo2"}

If the account has you blocked:
{"MSG":"MailBlocked"}

If you are not logged in:
{"MSG":"MailLoginRequired"}