I think that the main problem is that Log4Perl can only call the constructor with key-value pairs, unfortunately Mail:Mailer uses smtp as a scalar parameter.
The documentation mentions the following:
Since Mail::Send is a subclass of Mail::Mailer, you can change how mail is sent from this module by simply useing Mail::Mailer in your code before mail is sent. For example, to send mail via smtp, you could do:
use Mail::Mailer 'smtp', Server => 'foo.example.com';
I do not understand this part of the docu. Could one explaint it to me?

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