“Dangerous Attachments”

I use Windows Live Mail & have 2 email accounts.

Recently, when sending email attachments {PDF, JPG etc.}, I've been getting a warning that says: "[heading] Prohibited file type. The message states that "This message contains an attachment whose file type is considered dangerous. The file has been deactivated."  At the end of the message is a hyperlink to Get Help. I have not clicked on that link, in case this is malware.

Just before typing this message, I did a TEST message between my 2 Live Mail accounts & got that message on both the SENT & INBOX folders. I would appreciate advice if anyone else has encountered this problem.

THANKS