I want to reply to e-mail in my own handwriting. I am not thinking of Handwriting Conversion or Notes apps. Exchange client to be used to reply to emails - one approach is to sketch/free-writing in composer window or send it inline as image.Is it possibl

There are some third-party apps that feature handwriting capture, including a couple that have writing-to-text conversion, but I know of no email app that allows handwriting, so you would have to use an app that saves the handwriting as an image and allows that document to be emailed. Search the App Store for "handwriting" and you may find such an app.

As to restrictions, the only restriction I can think of, assuming the app in question does indeed allow a document to be emailed, would be the size of the attachment vis-a-vis any limited placed on message size by your email provider or that of the recipient.

Regard.

You would have to ask Apple Developer Support that question. If you're a iOS Developer Program member, though, Apple posts guidelines for apps to be offered through the App Store, so perhaps the guidance you need would be contained in that document.

Regards.