Mailbox.org has changed their mail-packages. They've framed these changes as being a "simpler and more flexible range of e-mail packages" of their previous options – that type of language pretty much always being a red flag. In doing this, they also offered existing customers a deal on this new package.
For example, the basic plan previously included all which you'd consider basic features, including disposable addresses, but also additional features like custom domain and external email integration. Now those features effectively costs an additional €2 (~US$2.5) a month. That's pretty damn shitty. Having access to disposable addresses should really be standard for a privacy oriented mail service.
They've also went ahead and locked the new goodies, like the new "Dark Mode" theme behind the same €3 "Standard" option. Sure, one might argue that it's an added bonus, but in my mind charging a premium for something that should really be standard for all websites and services at this point is downright scummy.