Delete user when session expires or exit the site but keep data in AcyMailing

That's my case:

user register to the site (no email activation) and I set-up and auto action to automatically login him soon after the registration process. The user navigate the site and do his stuff.

Now I want that when the user leave the site, or session expires, his account is deleted but at the same time I would keep his data in AcyMailing.

Is that possible?

Also, what will happens if the user do the registration process again after his account had been deleted? Any conflict with AcyMailing?

CB Auto Action does not provide an action to delete a user. You would need to use a Code action with PHP and use CBs API to load the user object and delete it. Best I can suggest is setup CRON to run the Internal Users URL within CB Auto Actions > Parameters then in your code check if they're logged (maybe doable in the condition by substituting the onlinestatus field). Deleting them on logout is only reliable if they log out. There is no trigger for if their session expires (that's not possible without constantly checking database sessions to see if they're expired).

As far as keeping AcyMailing data I have no idea. We didn't create AcyMailing so I can't begin to suggest what it does or does not do with user data when they're deleted from Joomla.