Hello @NLeVasseur,
Thanks for writing in! The link format you’re using should work, but the only thing I see that might be creating an issue is that your spaces are not “escaped,” which is necessary when setting up a mailto link. Try replacing any space with %20 and you should find that things function as they are supposed to. There are other characters that sometimes need to be escaped as well, such as ampersands, quotations, et cetera. You will need to ensure you have any of these properly output when setting up your subject query string.
If you are still experiencing issues after trying the method mentioned above, please provide us with a link to a live example so that we may see what is going on and if there is anything further you need to fix the problem.
Cheers!