Permanent sending Email

I was sending an email to an unkown adress. I get since 20 days everyday a message:
This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:
Unrouteable address
But I am not sending any more. Is there anywhere a automatic sending for mail in eMClient? I can’t find anything.

Thx’s

You will need to delete the message that is in the Local Folder Outbox. If Local Folders are not visible below your account folders, you can enable it by selecting Menu > Settings > General > General > Show Local Folders.