Open a digitally signed item that you received.
Click > .
Click the tabs to view information about the security certificate that was used.
The digital signature is verified when you open the item. If there are any concerns about the certificates that sign the item, a warning or an error displays immediately and the status bar of the item displays “Untrusted”.
If the digital signature was not verified, the security certificate might be invalid or the message text has been changed since the item was sent.