Fixes #61

Refers to #35

Fixes #51

Fixes #56

Refers to #50

That's the earliest place where setting up the mail logger is possible /
makes sense, so do it right then. Additionally, the check for SmtpHost
is redundant since it also done in the method called, so no need for it.

Refers to #35

This reverts commit 3f7fd9dc.

As intended and announced in the previous commit message.

Relates to #20

NOTE: this is known to fail for permission reasons, the commit is in
fact just to save the code and serve as an example (and to be reverted
right away).

Relates to #20

This way the service should now finally receive the system shutdown
events and be able to properly shut itself down.

Fixes #45

The name reflects the functionality much better.

Refers to #5

Fixes #5

Refers to #5

Fixes #36

Refers to #36

Refers to #36

Refers to #36

Refers to #36

Refers to #36

Refers to #36

Refers to #3

Allow setting the log level explicitly from "Warn", "Info", "Debug" or
"Trace" in the configuration.

Default is "Info", fallback for invalid settings is "Debug".

Fixes #34

Otherwise it will be missing when a grace cleanup email is being sent in
the startup phase.

Refers to #31

Fixes #31