[2.1.0] Checkmk Werk 16059 created: Fix possible failed notifications running in docker environment

Title: Fix possible failed notifications running in docker environment Class: fix Compatible: compat Component: notifications Date: 1695386294 Edition: cre Knowledge: doc Level: 1 State: unknown Version: 2.1.0p34 Werk #15941 already fixed failed notifications on appliances if one recipient had no Email address configured. We have now seen the same behaviour when running Checkmk in a docker container because Nullmailer can not handle such recipients.