Firefox Relay vs SimpleLogin: Which Email Masking Service Is Better

Firefox Relay is Mozilla’s email masking service, built into the Firefox browser ecosystem. SimpleLogin is an open-source alias service now owned by Proton AG. Both let you create aliases that forward to your real email address, hiding it from services you sign up with.

On the surface, they solve the same problem. Underneath, they are very different products with different strengths, limitations, and long-term implications.

Quick comparison

Free tier

SimpleLogin gives you 10 free aliases. Firefox Relay gives you 5. Both are limited, but SimpleLogin’s free tier is more generous and includes reply capability, which Firefox Relay reserves for paid users.

For casual use — creating a few aliases for services you do not fully trust — both free tiers work. But 5 aliases runs out fast if you adopt the one-alias-per-service approach.

Browser lock-in

This is Firefox Relay’s biggest limitation. The extension is Firefox-only. If you use Chrome, Edge, Safari, or any Chromium-based browser, you cannot use Firefox Relay’s inline alias generation on signup forms. You can still create aliases through the website, but the seamless browser integration — the main convenience feature — is gone.

SimpleLogin has extensions for Firefox, Chrome, Edge, and Safari. It works wherever you browse. For anyone who uses multiple browsers or does not use Firefox as their primary browser, SimpleLogin is the only option.

Custom domains

Firefox Relay supports one custom domain on its paid plan. SimpleLogin supports unlimited custom domains on its paid plan. If you own multiple domains or want aliases on different domains for different purposes, SimpleLogin is clearly more flexible.

Custom domain support matters because aliases on shared domains (like @relay.firefox.com or @simplelogin.com) are increasingly recognized by websites as alias services. Some services block signups from these domains. Aliases on your own domain look like regular email addresses and are never blocked.

Replying and sending

SimpleLogin lets you reply from aliases on both free and paid plans. When someone emails your alias, you reply through a special forwarding address, and the recipient sees the alias as the sender. Your real address stays hidden.

Firefox Relay only enables replies on the paid plan. Free users can receive through aliases but cannot respond without revealing their real address. This makes free Firefox Relay a receive-only service, which limits its usefulness for anything beyond throwaway signups.

Privacy and encryption

SimpleLogin offers PGP encryption for forwarded emails. If you provide your PGP public key, messages are encrypted before forwarding, so your destination email provider cannot read the content. Firefox Relay does not offer any encryption for forwarded emails.

Both services have privacy-focused parent organizations. Mozilla has a long track record of privacy advocacy. Proton (SimpleLogin’s owner) built its reputation on encrypted services. Neither monetizes user data through advertising.

SimpleLogin’s self-hosting option gives privacy-maximalists full control. Firefox Relay cannot be self-hosted.

Ecosystem integration

Firefox Relay integrates tightly with Firefox — it is built into the browser’s password manager and appears in autofill suggestions. If Firefox is your entire workflow, this is seamless.

SimpleLogin integrates with Bitwarden, 1Password, and Proton Pass. If you use any of these password managers (which most security-conscious users do), SimpleLogin generates aliases directly from the password manager during signup. This is more versatile than Firefox’s built-in integration because it works regardless of browser.

For Proton users specifically, SimpleLogin is bundled with Proton Unlimited subscriptions and integrates natively with Proton Mail and Proton Pass. The ecosystem is deeper than what Mozilla offers.

Phone number masking

Firefox Relay offers phone number masking on its paid plan — a masked phone number that forwards calls and texts to your real number. This is US-only but is a unique feature that SimpleLogin does not offer. If you need both email and phone masking from one service, Firefox Relay is the only option among these two.

The bigger picture: what neither offers

Both Firefox Relay and SimpleLogin are alias-only services. They create addresses and forward email. They do not filter what gets forwarded. This means:

• No spam filtering: Spam sent to your alias is forwarded straight to your inbox. Your destination provider’s filter is the only line of defense, and forwarding weakens that defense by breaking SPF.
• No quarantine: There is no way to review borderline messages before they reach your inbox (or your spam folder, where you will probably never see them).
• No MX-level protection: Neither service can protect a custom domain at the MX level. They are forwarding services, not email security gateways.
• No content analysis: No DNSBL checking, no AI classification, no virus scanning on forwarded mail. What arrives at your alias arrives in your inbox, minus whatever your destination provider catches.

The verdict

Choose Firefox Relay if you use Firefox exclusively, want phone number masking (US), and prefer Mozilla’s ecosystem. The paid plan bundles with Mozilla VPN, which adds value if you need both.

Choose SimpleLogin if you use any browser other than Firefox, want more free aliases, need custom domains, use a password manager like Bitwarden or 1Password, or want PGP encryption and self-hosting options. SimpleLogin is the more capable service by almost every measure.

Choose Cleanbox if you want aliases that actually filter what they receive. Cleanbox combines email aliasing with enterprise-grade spam protection — every message passes through Rspamd scoring, DNSBL checks against Spamhaus, Barracuda, and SpamCop, SPF/DKIM/DMARC verification, ClamAV scanning, and AI classification before reaching your inbox. Per-alias spam thresholds, quarantine with detailed reports, and MX relay for custom domains. Aliasing is just one feature, not the only one. For a direct comparison, see Cleanbox vs SimpleLogin.