When I create a new message, zimbra ask for my username and password to load the picture in the signature.
You see the picture in the signature then the login box apprear, if you click cancel you see the picture in the signature disappear.
But the recipient of the mail see the picture.

Does the same whether the briefcase is enabled on the account or not.

Any idea why zimbra ask for an authentification for something that is on an account who is already authentificated?

My version of zimbra is 8.0.4