Compatibility between the Letsignit Add-in (on Outlook Desktop) and the Antidote spellchecker is subject to the use of the latest version of Antidote.
Behavior observed if Antidote is out of date
When the Letsignit Add-in and Antidote are deployed on a user's computer and Antidote is run to correct an e-mail, the Letsignit signature already present in the e-mail may be inserted twice.
What should you do if you notice a double signature?
Update Antidote. To do this, launch Antidote, then access the “Help” > “Update search” menu.