Implements Mail::send() function using SMTP direct delivery
Either a comma-seperated list of recipients (RFC822 compliant), or an array of recipients, each RFC822 valid. This may contain recipients not specified in the headers, for Bcc:, resending messages, etc.
The array of headers to send with the mail, in an associative array, where the array key is the header name (ie, 'Subject'), and the array value is the header value (ie, 'test'). The header produced from those values would be 'Subject: test'.
The full text of the message body, including any Mime parts, etc.