Chrome will not open mailto links with over 2048 bytes in the parameters (like if you're sending a mass BCC to a list of students), even if you submit it as form data to a mailto action. Thanks to everything being based on chrome now, this means basically every browser except Firefox suffers from this issue.
Worth noting this is only the case in windows. My Mac and Linux test boxes worked fine, but that doesn't mean anything to me since something like 99.99% of my user base is windows.
Cybrespace is an instance of Mastodon, a social network based on open web protocols and free, open-source software. It is decentralized like e-mail.