Are HTML Comment Tags allowed in Email Templates?

For a couple of my custom email templates, I am using the <!–[if mso]> tag to target MS Outlook. These tags used to work fine, however currently the emails are not displaying correctly in Outlook, which makes me wonder if the tags are being stripped on the Auth0 side. Sending the same html email programmatically and from web clients displays correctly in Outlook. Can anyone clarify whether these tags are allowed in the Auth0 email templates?