I followed this guide and can partially confirm that it solves the problem. Emails to logged in users or agents are now handled and delivered correctly.
Unfortunately, the problem still exists for external users. When Chatwoot is embedded on the website, visitors can leave their email address before the conversation starts. This will additionally send replies to the visitor via email in case the visitor leaves the site in the meantime. These emails will still be sent from the wrong email address. This is clearly evident from the Cloudron email log.
As a result, the problem unfortunately persists. Is there a solution for this?