I have an extra field for icons with social media for my users and the email icon doesn't work because the mailto links generate some kind of weird code instead of the actual link. Any ideas?

voxinteractif.com/v2014/fr/l-agence

Hover the team's member pictures to see the social media icons.

There is no mailto link in k2 extrafield type, did you add on your own ? You could try disabling the joomla email cloak plugin.