How can I delete emails for a specific email account older than X days in Exchange 2003 from the server? I would like to do this from the server, not from the outlook client.
You could use the tool ExMerge. Here is a decription how to delete messages on the server using that utility:
You can download Exmerge in Microsoft's Download area.
Here is a screenshot of the selection criteria (by date):
You can use the Mailbox Manager Settings in the Recipient Policies to set a retention limit on email messages.
You can read the steps on how to accomplish this in KB319188.