Gmail – block incoming emails to the Gmail

Check Penango, it's "the successor to Gmail S/MIME". (Edit - Dead link to old index page replaced by download page for version for free Gmail. Support for Google Apps and paid-for Gmail is a pay-for product.)

Penango makes secure e-mail easy to use, simple to manage, and accessible everywhere. We make a suite of web browser extensions that let you send and receive authenticated and encrypted messages directly in your webmail environment.

If a filter with criteria * is working for you with the exception of the sent messages, you might try

* AND !is:sent

Alternately, see if your wildcard will cause received mail to fall within scope of the following

to:me

I don't know offhand if to:me triggers on your primary address, or uses a more comprehensive method of matching.

Incidentally, what are you trying to accomplish by starring all incoming messages? Some kind of "sticky" indicator of read/unread (or "handled") status?