That’s correct, subaddressing is a ubiquitous feature. That’s not what I was talking about.

Port87 is built entirely around subaddressing. The “bare” address doesn’t even go through to you. It also labels email automatically based on the subaddress, and you can control setting per label, like mark-as-read and notifications. You can also have screening on any of your labels, so that only humans can email you there. Subaddressing is not an optional afterthought, it is required and how the system works.

Port87 does not have an inbox. (Which I found out while creating it is something that basically all open source email software expects to exist.) It has an “Aggbox”, which is not a real place, but a filter for which labels you want to see when you open the app.

Port87’s search box is, I would say, the most powerful email search feature of any email service. It’s nearly as powerful as a straight up SQL query.

So yeah, I would say it’s unique among email services.

Also, simple login and addy aren’t really email “providers”, they’re more accurately called forwarding services. Email provider, or officially “mail service provider”, is specifically the term for an email service that sends, receives, and stores email.