Hi @Ketangp - its not actually possible to track a mailto: link since it doesn't open a web browser to the Campaign tracking server. mailto: and tel: links are handled by the mail client natively on the user's local machine or within the browser client.
There are some workarounds you can do where you link to a page that opens a mailto: link using Javascript, but the CX on something like that is questionable, but at least it is tracked.
Cheers
Darren