In my app I have automated e-mails reminding applications to complete the next step in the interview process. The e-mail has an opt out link which, when clicked, should hit
The method option on link_to works because your app includes some javascript that intercepts clicks on the link. That javascript creates a form with the correct method (adding an input element for request methods browsers don't support) and supports that.
This won't work in an email: your site's javascript isn't present and email clients don't usually run javascript.
Including an actual form works in some cases, but very frequently doesn't (or displays scary warnings) - see this question for example.
There's not much alternative to just having a plain "get" link unfortunately (you could of course have that go to a confirmation page where you have a button/link that will fire a post request).