Ask your system administrator for details. At least if your user id does not contain your name, apply a signature identifying who you are. I for one find it somewhat impolite to get emailed queries from users who do not even care to identify themselves. In fact the probability of getting a useful answer, or an answer at all, is severely decreased if you don't identify yourself. Use the same courtesy as you would in ordinary non-electronic communication.
Signatures are an issue that occasionally invoke quite puritan views.
For example, some users on the Usenet hold a firm view that any reference in a signature to the person's employer or to any material available from the sender always is tantamount to spamming. This is taking things a bit far. On the other hand, whatever would be improper within the body of a message is still as improper in a signature. It causes many users to use email address munging and to put their true email address in their signatures only in a human readable format. For more information links on this please see the material my Foiling Spam with an Email Password System .