Cleanbox vs Firefox Relay: Email Protection Beyond Aliasing

Firefox Relay is Mozilla’s email masking service. It generates random forwarding addresses so you do not have to share your real email when signing up for websites. It is simple, privacy-focused, and works well within Firefox.

Cleanbox also creates email aliases. But aliasing is one feature among many. Cleanbox is a complete email protection platform that combines aliasing with multi-layer spam filtering, virus scanning, quarantine, contact management, and MX relay for custom domains.

This is not a comparison between two equivalent products. It is a comparison between a focused aliasing tool and a full email protection stack that includes aliasing. Understanding the difference helps you decide which level of protection you actually need.

Quick comparison

What Firefox Relay does

Firefox Relay generates random email addresses like k7xm3@relay.firefox.com. When a website asks for your email, you give it a Relay address instead of your real one. Emails sent to the Relay address are forwarded to your real inbox. If the address starts receiving spam, you disable it.

The free plan gives you 5 aliases with forwarding only (no replies). The paid plan ($3.99/month, bundled with Mozilla VPN) adds unlimited aliases, one custom domain, reply capability, and phone number masking (US only).

Relay works best as a Firefox feature. The browser extension auto-suggests creating aliases on signup forms. If you use Firefox as your primary browser and want quick address hiding for web signups, Relay is convenient and well-integrated.

What Firefox Relay does not do

Firefox Relay is a forwarding service. It takes email addressed to your alias and sends it to your real inbox. That is the entire product. It does not look at what it forwards. Specifically:

• No spam filtering: Spam sent to your Relay alias is forwarded to your inbox. Mozilla does not scan, score, or filter incoming email. Whatever arrives at the alias arrives in your inbox (minus whatever your destination provider catches).
• No authentication checking: Relay does not verify SPF, DKIM, or DMARC on incoming messages. Spoofed email from forged senders is forwarded without verification.
• No virus scanning: Attachments are forwarded without malware scanning. If someone sends a malicious file to your Relay alias, it reaches your inbox.
• No quarantine: There is no holding area for suspicious messages. Everything is either forwarded or not. There is no way to review borderline messages before they reach your inbox.
• No contact management: Relay does not track senders, categorize contacts, or let you whitelist or block specific addresses per alias.
• No MX relay: Relay cannot act as your domain’s MX gateway. It is an aliasing service, not an email security gateway.

And because forwarding breaks SPF authentication, your destination provider’s filter has less signal to work with. Spam that Gmail would catch when sent directly can get through when forwarded via Relay.

What Cleanbox does differently

Cleanbox creates aliases the same way Relay does — you get an address, it forwards to your real inbox. The difference is what happens between receiving and forwarding.

Multi-layer spam filtering

Every email arriving at a Cleanbox alias passes through multiple detection layers before forwarding:

1. Authentication: SPF, DKIM, and DMARC are verified. Spoofed senders that fail authentication are flagged or rejected.
2. Reputation: The sender’s IP and domain are checked against Spamhaus, Barracuda, and SpamCop. Known spam sources are blocked before content is even analyzed.
3. Content scoring: Rspamd applies hundreds of rules to the message — header analysis, URL checking, pattern matching, Bayesian classification. Each rule adds or subtracts from a total score.
4. AI classification: An AI classifier analyzes the message content for phishing patterns, social engineering, and AI-generated spam that rules-based systems miss.
5. Virus scanning: ClamAV scans attachments for known malware before forwarding.

Only messages that pass all layers are forwarded to your inbox. Spam is rejected or quarantined.

Quarantine with transparency

Borderline messages — those that score above your spam threshold but below the rejection threshold — are held in quarantine. Each quarantined message includes a detailed spam report explaining exactly which rules triggered and why the message was flagged. You review and release false positives with one click. Nothing is silently deleted.

Per-alias control

Each alias can have its own spam threshold. A newsletter alias that receives marketing email can have a lenient threshold. A personal alias used for important communication can have a strict threshold. A catch-all alias can have the most aggressive filtering. Relay treats all aliases identically.

Contact management

Cleanbox automatically categorizes contacts into 20 categories (Shopping, Finance, Social, Travel, etc.) and lets you assign one of 5 states to any contact: whitelist (always deliver), block (always reject), mute (deliver silently), prioritize (highlight), or unset (default filtering). Known trusted senders bypass content scoring. Known spammers are blocked immediately. Relay has no concept of sender trust.

MX relay for custom domains

For custom domain owners, Cleanbox Relay goes beyond aliasing. Your domain’s MX records point to Cleanbox, which acts as the first line of defense for all email to your domain. Spam, viruses, and threats are filtered at the infrastructure level before reaching your mail server. Your server’s IP stays private. Relay does not offer anything comparable.

When Firefox Relay is enough

Firefox Relay is a good choice if:

• You only need aliases for throwaway signups where you will not receive important email
• You use Firefox as your primary browser and want native integration
• Your destination provider (Gmail, Outlook) handles spam filtering adequately for your needs
• You want phone number masking (US)
• You prefer a Mozilla-backed, open-source solution

For hiding your address during web signups that you do not care about, Relay works fine. The spam that gets through is an annoyance, not a crisis, because nothing important arrives at those aliases. For a comparison of Relay with another aliasing-only service, see Firefox Relay vs SimpleLogin.

When you need Cleanbox

Cleanbox is the better choice when:

• You receive real, important email through your aliases (business, personal, financial)
• You own a custom domain and need MX-level protection
• You want spam filtered before it reaches your inbox, not just hidden behind aliases
• You need quarantine and review for borderline messages
• You want per-alias spam thresholds and contact management
• You use multiple browsers or platforms (not just Firefox)
• Your destination provider’s spam filter is not catching enough

The fundamental difference: Firefox Relay hides your address. Cleanbox hides your address and protects what arrives at it. If aliasing is all you need, Relay works. If you need protection, Cleanbox is the more complete solution. For comparisons with other alias-focused services, see Cleanbox vs SimpleLogin and Cleanbox vs addy.io.