Mails don't reach Zammad and can't be sent

Steps to solve this issue:

1. Reboot server - emails were only processed briefly in the inbox, 5 minutes later no tickets arrived again
2. approx. 15 minutes later: Service “Zammad” was restarted on the server, emails were only processed briefly in the inbox, 5 minutes later no tickets arrived again
3. approx. 25 min Later: Reboot server again, emails were only processed briefly in the inbox, 5 minutes later no tickets arrived again
4. Restore the Elastic Search. After 10-15 minutes, everything was slowly processed

It is noticeable that emails from mailboxes (which are integrated in Zammad) should be automatically moved to the deleted elements. With the current phenomenon, they simply remain in the inbox and Zammad simply doesn’t pick up the emails.