I've been using Thunderbird without incident for years. However, of late, the spam filter "if it isn't in my personal address book/collected addresses" isn't working properly. For the first time ever I've got spam in my inbox and--less often--emails from my address book going to Junk Mail or the Trash. Have the spammers developed a new technique I don't know about? The from addresses aren't familiar, aren't in my address book, and aren't from my own email (I've seen that a couple of times over the years).

Please advise.