What InvisibleCRM Support Team Guru say:
Do it with SalesDesktop
Working offline with SalesDesktop you get all the possibilities of working with Salesforce.com items, including sending them with saved emails to Salesforce.com.
Just write a letter and select the “Send and Save” option from the SalesDesktop toolbar.
The letter is dropped in Outbox, waiting for an online connection to be sent (screenshot #1).
At the same time, this letter is saved into SalesDesktop and will be synchronized with your Salesforce.com when you go online (screenshot #2).
Attached Screnshots: