Sorry if I sounded dismissive Vespine. Seeing that others have received this email, it can't be just a leg-pull.
Not suggesting you ignore the email, but it brings up lots of questions. First is the long retrospectivity of it, on what in essence is a trivial matter in Customs terms (why don't they do this with eyepiece solar filters!! lol). Then there is a Federal/State jurisdictional matter. Then there is the issue of actual legality in Victoria, according to the interpretation offered by Ken. Then there is the issue of continued availability on ebay and in retail shops in Victoria. All seems very strange.... a clamp-down beginning with "ancient" purchases on ebay.
If it's ridgy-didge, I can't imagine that the AFP is accessing ebay personal information (well, it may, but could or would it use it in cases as trivial as this? It ain't terrorism!). Check ebay's Terms of Service maybe. Perhaps it came from the Customs declaration attached to your delivery. So does that have your email? I don't think my own OS deliveries have had my email address. Does the AFP have the resources to track down what is probably tens of thousands of these little blighters all over the country, purchased from all sorts of outlets?
I think you should contact the AFP, but not by reply to the email. Then hopefully things will be cleared up.
Anyway, good luck Vespine, & keep us informed!
Cheers -