@rodneylives The question is if the user has a mail program that they use and that is configured for their email. Most people use webmail now-a-days and while I have seen webmail clients ask to register itself for mailto links, I'm unsure how common it is that people go though with it.
I think it would work more often on mobile. People usually have an email app that is setup. However, Firefox for Android has problems with mailto links π
https://support.mozilla.org/en-US/questions/1424189
@quirk Ah, I don't know what happens, in my case, if a mail client isn't set up at all.