Please Improve advertisers' policy on your media channels:
it exists several advertisers/media associations which have set minimum rules/policies to apply ethical advertising campaigns.
respecting them is a minimum as far as your advertisers contract with you, you are indirectly responsible of the content they publish on your medias: email application included.
you are a strong and rich Media agency above all.
providing free service doesn't leave you without respect toward your customers.
more than on any other media aka Google, Facebook we detect phishing, scams and fraud within even personal email-inboxes.
As far i hope this will end soon, otherwise you are endangering the big effort you developed so far regarding UX/UI of you email services among other apps.
Looking forward a more strict policy related to your Ad/ sponsored contents.