system sends empty emails to myself - should I worry?

[Micha Feigin <michf@post.tau.ac.il>]

On my home server I get about once every couple of days an empty email
sent to myself as the regular user. The headers seem to indicate that
it originated on the local machine but nothing else.

I have smtp access I once setup there but currently its blocked to the
world using the firewall.

chkrootkit doesn't bring up anything suspicious.

Should I be worried about this? Any ideas on tracking down what is
trigering these emails?

The system is woody running on an old world mac (beige G3).