This is interesting timing - I just built something adjacent to this problem. If you're on the SES → S3 pipeline specifically (routing incoming mail to an S3 bucket), I made QuickMailBites (github.com/bonskari/quickmailbites) - a Flutter desktop client that reads directly from S3. It won't replace a full mail server setup like Inbox.camp, but if you just want a lightweight reader for mail that's already being stored in S3, it's pretty lean.