QDesktopServices::openUrl fails for "mailto:" with gmail

When I use QDesktopServices::openUrl with a "mailto:" link to open the user's email client, if works if that client is something like Outlook. But if the client is Chrome, configured to open gmail, the entire contents of the body all end up in the 'to' field of the email.

My code is:

QDesktopServices::openUrl(QUrl("mailto:" + to + "&subject=" + subject + "&body=" + body, QUrl::TolerantMode));

The subject and body is mostly plaintext, along with some "\n" line endings. I have also tried with a simpler body that has no "\n" – just very plain text. Same issue.

I have tried encoding the to, subject, and body prior to executing the code above, but with no help as well.

For the code above, with the following QStrings:
to: "support@csaim.com"
subject: "CedarsReport Bug Report"
body: "An unhandled error occurred in preview.ts: updateWatchers"

the following ends up in gmail's "to" field:

support@csaim.com&subject=CedarsReport Bug Report&body=An unhandled error occurred in preview.ts: updateWatchers