You could probably cobble together a POP server on top of S3 pretty easily (e.g. using something like https://github.com/femto113/node-pop3-emitter https://gith

You could probably cobble together a POP server on top of S3 pretty easily (e.g. using something like https://github.com/femto113/node-pop3-emitter https://github.com/femto113/node-pop3-emitter which I threw together a couple years ago for a related purpose). I'm not sure if you can get it to work in Lambda though because the POP3 protocol needs sockets, but you could definitely get it to work in a simple container in Fargate (so still "serverless").