I've been using Fastmail's Masked Email for years, but using it outside of the Fastmail application has required using the sorta-janky implementations in the browser extensions for 1Password or Bitwarden. When I needed to generate a new masked email address, I would have to hope that 1Password would realize I needed a disposable email address, otherwise I'd be logging into Fastmail and hunting through the Settings to mint a new disposable address.

Now with Masked Email Manager, I've got all my masked emails at my fingertips any time in Firefox. I've been waiting years for this.