Answer:
Your current mail address is "me @ my-domain.com". Set up a Gmail
account (me.my-domain @ gmail.com) and forward your mail to it. Create
a new account on your server (me-1 @ my-domain.com) and have your gmail
account forward mail back to me-1. Gmail will not forward spam. It may
flag some senders erroneously as spam, but you can teach it how to
handle that so it doesn't happen in the future. Point your e-mail
client to retrieve mail from the new me-1 account. Flush your original
"me" account once in a while.
That's how you perform free spam filtering on your own mail server - by
routing it through gmail.