Rule to deleate emails based on words in body keeps generating an error

[Sandy]

A rule I created to permanently deleate emails based on words in the
body keeps generating the following error and turning the rule off:

Rule in error.
You do not have sufficient permission to perform this operation on
this object...

A similar rule based on words in the subject works just fine, but that
will not handle many of the emails I want to trash.

Any ideas?

THANKS!