Is it possible to convert e-mails in the iPad and iPhone app to tasks - and how?
Not directly, but yes. You can't link to mails the way you can on the desktop using our Gmail or browser extensions, but you can actually send these mails through any platform or device to a certain Todoist project.
To do so, right-click on a project and choose "Email tasks to this project" (on the desktop). This will show you a new window containing a unique email address for this project (which you could save as a contact) and more information about how this feature works.