Домик АдминовНе работает почта

labbit@lostmagic.ru посылаю письма с вопросом о платной услуге с разных ящиков c mail.ru, возвращается и пишет This is the mail system at host mx.labbit.ru.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

The mail system

(expanded from ): user unknown

Как связаться с администрацией.