DigitalOcean to create a managed Email-As-A-Service offering for users, so they can just buy it from you and create/consume/delete/upscale/downscale/administer email mailboxes and redirections, including configurable antivirus and antispam capabilities.
Rationale for this suggestion: Putting together a reliable, secure and easy-to-manage email handling software stack (and maintaining it over time) is quite hard, so this service would sell well for sure.
If you want to sneak peek this, have a look at what Ionos offers to its VPS customers for free :-)