Hidden Field from user email field

Hi.
I’m using the hidden fields within the “to:” field in the mail tab. As the hidden field comes from the user profile e-mail address, which is registered at the sign in process and not with during the form fill, I keep getting this “Invalid mailbox syntax is used.” note.

Is there a way to avoid this?
I know this error appears to prevent e-mail fields within a form not to be filled but, what about other sources?

Should I ignore and live with this false positive?

Thank you.
Best regards.