Sign Method
Signs the message.
Syntax
psmtp.sign([callback])
Callback
The 'callback' parameter specifies a function which will be called when the operation completes (or an error is encountered). If the 'callback' parameter is not specified, then the method will block and will not return until the operation completes (or an error is encountered).
The callback for this method is defined as:
function(err){ }
'err' is the error that occurred. If there was no error, then 'err' is 'null'.
'err' has 2 properties which hold detailed information:
err.code err.message
Remarks
This method signs the specified message.
The message is signed with the private key specified in the Key* properties.
When signing, the following properties may be used to further configure the class: