By now I am convinced this is useless. If you provide an mailto link the email must be readable by the browser one way or the other. You can confuscate it, use JS to uncrypt it, but in the end it’s easy to break. To avoid getting your email out a form is probably the only solution. I at least don’t plan to integrate a solution for now.
Spam protection is a task of the e-mail provider you decide to use. And in the very end, whatever fancy encryption you might add to the e-mail link it will always be “readable”, since the browser in the very end displays the configured mail client.
From my experience, with a public e-mail, is no changes at all in the amount of spam that have made it way to my e-mail inbox. No spam messages have made it’s way, thanks to the spam protection used by my e-mail provider (in my case Google Apps).
From a usability perspective, it’s easier to copy a e-amil by right-clicking it and copieng the e-mail (supported by most moderne browser, that identifies a mailto: link)
Well there’s networkteam/neos-mailobfuscator if you want to try your luck. It has a very simple obfuscation strategy that can prevent the most simple forms of scraping.