Posted by abelsromero on May 14, 2020; 7:16am
URL: https://discuss.asciidoctor.org/mailto-hyperlink-incorporating-spaces-newlines-in-email-body-tp7996p7998.html

Not a proper answer but as a workarround I have been using the url format and it seems to work.
I am opening from HTML and PDF using Thunderbird.

mailto:me@mail.org?subject=Title%20with%20spaces&body=This%20is%20my%20body[me@mail.org, window="_blank"]