Query4All.com
Mail_feedback
Data generated from past analysis.
https://support.google.com/mail/answer/9212652?hl=en&co=GENIE.Platform%3DDesktop
https://support.google.com/mail/answer/9212652
https://www.apple.com/feedback/mail.html
https://www.facebook.com/p/Mail_feedback-100070317817715/
https://aether.lbl.gov/www/feedback.html
https://github.com/nextcloud/android/issues/59
https://community.constantcontact.com/t5/Get-Help/Mail-Feedback/m-p/389568
https://mopinion.com/product/mopinion-for-email/
https://github.com/agragregra/uniMail