Problem with file attach p7m

Hi,if I receive one mail from internet a message with file attach *.p7m extention, the message arrive, in my mail box, without file attach.

I stress that i receive all others formats normally.

why this?

someone can help me ?

Subject: Problem with file attach p7m

A p7m file extension is a file that has been encrypted with Entrust. We had to load at least 6.5.4 as a client for anyone needing to use Entrust. We don’t have anyone reading Entrust encrypted attachments through a browser.

Hope this helps, some.