Opt-in Thank You Pages - Setting Expectations

When someone signs up for your email newsletter, your "Thank you for signing up" confirmation page should set expecations (especially if you're using the double opt-in method, and people should be expecting a confirmation email and activation link). You can use the "thank you page" to tell recipients how often they should expect your newsletters, and also to ask them to "whitelist" your email address (so you won't get mistakenly spam filtered). Incidentally, MailChimp lets you totally customize your "opt-in confirmation" page any way you want.

I recently signed up for an email newsletter, and thought this was a nice example of an opt-in thank you page, with lots of explanation about spam filters and whitelisting.