To deactivate your autoreply, first log in to your Posteo account. Then follow these steps:

1. Open Settings.
2. Click on My Account.
3. Open the Autoreply menu.

4. Uncheck the box next to activate autoreply.
5. Click Save.

Done. You have deactivated autoreply. Until you set up a new autoreply, no more emails sent to you will receive an automatic response.