As far as I understand, I cannot easily iterate through the users in Amazon Cognito.
Is there a way that I can send all of my users an email on updates for my app (possibly through SES)? Or should I not use Cognito because it is not built for this purpose.
As you suspect, AWS does not intend Cognito to do mail-list management; only transactional emails.
From what I've seen, it's pretty common to manage mail-outs (including product updates) through something like MailChimp or HubSpot, which include additional tools to track user engagement, manage campaigns, and handle the various data protection requirements that different regions expect of companies.
That said, for relatively modest numbers of users (think 100s) you can get away with using ListUsers with a lambda and SES.
