I'm not sure that I completely understand. Do you mean that auntiehelen@sleepinglion.com can be either a normal address or a forwarding address, and if the latter then anti-spam is turned on automatically? It would just be a pain I think, if you had to use one account to read mail and another to send.
A lot of older addresses were intended for what we used to call offline readers (OLRs), or in more modern terms for you to connect with an email client (e.g. Outlook), and download mail, rather than to use as Webmail. I still do that. One of the side-effects is that, when you do get around to signing in to Webmail, you find that they've added new features and controls that you didn't know about. Is there any chance you could just sign in and turn on anti-spam?
I've got a Compuserve account that I've had since the early 90s. That too was originally paid, but now (owned by AOL) is free.