One of the reasonably good weapons in the war against spam is never giving companies your real, core email address but instead creating different individualized email addresses for each place that requires an email address from you. When email addresses inevitably leak or get abused, you can immediately finger the culprit simply by what email address the crud is coming in to. If you start getting spam email to 'you.vendor1@...', well, you know who to blame.

There are a lot of ways to do this, depending on exactly where you have your email; some email providers let you add arbitrary suffixes to your email address after a special character, for example. But however you do this, there is an obvious but important feature you should try to have if at all possible: you should be able to turn off such addresses. Generally such turned off addresses should be rejected during the SMTP transaction, although in some circumstances you might want to turn them into spamtraps instead.

The reason why is pretty straightforward. As I can say from personal experience, after a while at least some of your addresses will become so contaminated that the spam they get is no longer at all interesting. Once an address gets leaked badly enough that the advance fee spammers and the phish spammers and so on get their hands on it, well, there's no end to them.

(I don't recommend that you immerse yourself in the (anti-)spam world, not unless it's your profession. Trying to track advance fee fraud and phish spam is an endless task.)

Most systems for individualized addresses can probably already do this, but if you're building one (for yourself or for a general population), remember to include this. It may take some extra work, but you'll thank yourself in the long run.

(The simple approach is to make the address not exist any more, so it's rejected at SMTP time the same as any other nonexistent local address. The more advanced one is to still reject at SMTP time but to keep track of things like how many attempts to mail it there were recently and so on, and let people see this. Although, honestly, I'm not sure how many people will really care about that. You probably do want to keep track of old turned off addresses so that people get a warning if they're recreating them by accident.)