Masked Email Manager
Guide
Fastmail Masked Email vs. Apple Hide My Email
Both hand a signup form an address that isn't your real one. The difference is in who can make one, where you manage the list, and what happens once you own more than a handful.
The same idea, two implementations
A masked address forwards to your real inbox, and a service that only ever had the masked one can't reach you once you switch it off. Fastmail Masked Email and Apple's Hide My Email both work this way, and both let you reply from the masked address itself rather than exposing your real one in the process.
Where they differ
Hide My Email comes in two tiers. The relay address that Sign in with Apple hands you at a supporting login screen is free and unlimited on any Apple ID. Making your own, for a form that just wants an email address, needs an iCloud+ subscription. Fastmail Masked Email is included with every paid Fastmail plan, no separate add-on.
Hide My Email is generated from Safari's autofill, the Mail app, iCloud settings, or iCloud.com: all four sit behind an Apple Account with two-factor authentication turned on, but only iCloud.com runs outside Apple hardware, from any browser. Fastmail Masked Email comes from Fastmail's own web app, its browser extensions, or an app like this one, needing only a Fastmail account. Once created, either address just forwards mail, and works on any platform from there.
Fastmail publishes an API for Masked Email. That's what lets a third-party app show the full list with descriptions and one-tap blocking, and it's why more than one such app exists. Apple hasn't published an equivalent API, so Hide My Email addresses are only manageable from Apple's own Settings or iCloud.com: each one gets an editable label and note, and iCloud.com adds search once you have five or more, but there's no way to manage the list from anywhere outside Apple's own interfaces.
Which one to use
If you're already paying for Fastmail, its Masked Email costs nothing extra and travels with the account regardless of which device or OS you're on next. If you're in Apple's ecosystem and don't want another mail provider, Hide My Email covers the same signups without leaving Settings, at the cost of an iCloud+ subscription for anything beyond the Sign in with Apple relay. Nothing stops using both: they're addresses, not accounts, and a service only ever sees the one you gave it.
Already on Fastmail? The create guide covers generating your first address, and Masked Email Manager keeps the whole list a swipe away on your phone.