All mails sent to the special Postmaster addresses are saved into the
MIREKA_HOME/postmaster directory. They are sent to their assigned
destination as well. There are two types of postmaster addresses. In the
first form, no domain is specified. This is always accepted. In the second form,
domain part is also specified. These are only accepted if the domain is a local
domain. This feature is useful for debugging. The saved file shows the content
of the message before any processing. The mails are saved even if an error
occurs later in the processing chain, e.g. the back-end server cannot be
connected in proxy mode.
You may need to clear the directory occasionally.