Creates an attachment from a file.
int AttachFile(const QString& qsFilename);
Use this method to create an attachment from a file. Use Attachments property to provide further attachment details.
The method returns the index of the new attachment in the Attachments list.
This method returns an Integer value; after it returns, call the GetLastErrorCode() method to obtain its result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message.