We are trying to be transparent about that - so the following is also mentioned in the installer wizard :)
TLDR; We are not sending any(!) data of your inbox to our servers. And we will never do!
When you install yasoon, there is a little registration wizard at the beginning which will register an account at our server. This is simpy to confirm that you are the owner of your e-mail address (we are sending an automated registration email afterwards). In addition, you can give a small profile which will make the UI a little more user friendly (profile image, etc.). This is also transferred to our server. However, this is completly optional and is currently not used anywhere. We may offer some collaboration features in the future, but this will also be opt-in to share your profile.
Besides that, we only log some serious errors which occur in our runtime, but we never send any data of your inbox out! No e-mail data, no tasks, no calendar items!
//Edit: In addition, the remote logging is disabled when you turn on the Dev mode, because we are only interested in production errors.