Does AppSheet have any ability to integrate with an email service (e.g. Mailchimp, Constant Contact, etc.) standing alone or with a 3rd party solution like Zapier?
Mailchimp has a rest API connection and at least you could create that connection with scripting.
I expect very soon (before end of this year) we’ll have an integration option to set up your own MailChimp service. At this moment, you’d need to use a Webhook action and wire up the JSON in it yourself.