Extend activity eg : Outlooksend Mail

I would Like to extend an existing activity. Do someone know if it’s possible?
I created an activity that extend code activity alright.
Now I want to extend an existing activity, like Send OutlookMail message for example ?
Is it something possible or it’s protected…

My purpose is to add some input and option to the existing activity (Linked attachment(images), mailMessageObject, ect…)

If I can’t, an other question would be how to send an HTML email message with images embeded in the body and not referenced as attachments (c# .net → alternateView.LinkedResources.Add ).

Before you ask not it’s not a duplicate of This post


Without any Linked ressources all the images are taking out and sent to the bottom of the mail in IOS for example.

Thanks a lot