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Productivity · head to head

Fastmail vs Mozilla Firefox

Fastmail logo

Fastmail

Productivity

Paid email hosting with custom domains, calendar and contacts, run without ad-based revenue

From
$3/month
Rated
-
Full reviewWebsite
Mozilla Firefox logo

Mozilla Firefox

Technology

An independent web browser with its own rendering engine, funded almost entirely by search placement deals.

From
Free
Rated
-
Full reviewWebsite

The short version

  • Only Mozilla Firefox has a free tier, so it costs nothing to try first.
  • Each has a real cost: Fastmail it does not provide end-to-end encryption by default, so users specifically wanting zero-knowledge mail should compare it against Proton Mail or Tuta rather than assume parity.; Mozilla Firefox roughly 85 per cent of Mozilla's revenue comes from search default placement deals, overwhelmingly with Google, so the organisation that competes with Chrome depends on Chrome's owner for its funding and any renegotiation lands on Firefox's engineering budget within a quarter.
  • They diverge on capability: Fastmail covers Custom domain hosting, Mozilla Firefox covers Gecko engine.
  • Prices and features above were last checked on 1 September 2026.

Where they differ

Only the attributes on which Fastmail and Mozilla Firefox actually diverge.

Attributes where Fastmail and Mozilla Firefox differ
AttributeFastmailMozilla Firefox
Starting price$3/monthFree
Pricing modelPer user per monthUnknown
Free tierNoYes
PlatformsWeb, iOS, Android, macOS, WindowsWindows, macOS, Linux, iOS, Android
CategoryProductivityTechnology
FoundedUnknown2004

Identical on both: user rating (Not yet rated).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Fastmail

  • Custom domain hosting
  • Masked email
  • Unlimited aliases
  • Integrated calendar and contacts
  • Migration tools
  • JMAP support

Only in Mozilla Firefox

  • Gecko engine
  • Full webRequest blocking
  • Total Cookie Protection
  • Container tabs
  • Extended Support Release
  • policies.json and ADMX
  • Built-in developer tools
  • Firefox Sync

What people use each for

The jobs each tool is most often brought in to do.

Fastmail

  • Someone who wants their email address tied to a domain they own rather than a free provider they do notnot Mozilla Firefox
  • A small business wanting hosted mail on its own domain without running mail server infrastructurenot Mozilla Firefox
  • A person leaving Gmail specifically to stop an ad-funded provider processing their mailnot Mozilla Firefox
  • A household migrating several accounts to one paid provider with shared billingnot Mozilla Firefox

Mozilla Firefox

  • Web development where you need to test against a non-Chromium engine before shipping, because Chromium-only testing hides real bugsnot Fastmail
  • Users who require a full-strength content blocker, which Chrome's Manifest V3 no longer permitsnot Fastmail
  • Managed fleets that need a browser on a slow release cadence with Group Policy control, using the ESR channelnot Fastmail
  • Handling several accounts on the same service at once through container tabs, without separate profiles or private windowsnot Fastmail

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Fastmail

  • It does not provide end-to-end encryption by default, so users specifically wanting zero-knowledge mail should compare it against Proton Mail or Tuta rather than assume parity.
  • Moving to Fastmail is a real migration with DNS changes for a custom domain, unlike installing a client such as Spark or Bluemail over an existing account.
  • There is no free tier at all, so a user just wanting to try it commits to a paid trial rather than a permanently free option.
  • Storage limits on the entry Basic plan are modest next to the free allowance Gmail gives, and heavy attachment users will need Standard or above.
  • Being based in Australia means it falls under Australian data access law, which some privacy-focused buyers weigh differently from Swiss or German jurisdictions used by Proton Mail and Tuta.

Mozilla Firefox

  • Roughly 85 per cent of Mozilla's revenue comes from search default placement deals, overwhelmingly with Google, so the organisation that competes with Chrome depends on Chrome's owner for its funding and any renegotiation lands on Firefox's engineering budget within a quarter.
  • Desktop market share sits at a few per cent, so commercial sites are tested against Chrome and Safari and a Firefox-only rendering or WebRTC bug is triaged as low priority by the site owner, leaving you with the workaround.
  • On iOS and iPadOS the browser is a WebKit shell required by Apple's rules, so it delivers the interface and Sync but none of the engine, extension or tracking-protection behaviour that make Firefox worth choosing on desktop.
  • Mozilla declines to implement several hardware-facing APIs on principle, including WebUSB, WebSerial, Web Bluetooth and WebHID, so a web application that talks to a device simply does not run and no configuration flag changes that.
  • Enterprise management is limited to policies.json and ADMX templates; there is no first-party equivalent of Chrome Browser Cloud Management, so fleet-wide reporting on versions and extensions requires third-party tooling you have to buy or build.
  • Mozilla repeatedly ships decisions its own user base objects to, such as enabling Privacy Preserving Attribution by default and the 2025 Terms of Use rewrite, and reversals arrive after the news cycle, so deploying it on a privacy argument means owning the communications work each time.

Pricing, plan by plan

Fastmail

$3/month
  • Basic$3/month
    • 6GB storage
    • No custom domain support
    • Core mail, calendar and contacts
  • Standard$5/month
    • 60GB storage
    • Custom domain support
    • Masked email and aliases
  • Professional$9/month
    • 150GB storage
    • Multiple custom domains
    • Priority support

Mozilla Firefox

Free

No published plan breakdown. See the Mozilla Firefox review.

Which should you pick?

Choose Fastmail if

  • You need custom domain hosting.
  • You work on Web, iOS, Android, macOS, Windows.
  • You also want masked email.
Fastmail review

Choose Mozilla Firefox if

  • You need gecko engine.
  • You want to start without paying.
  • You work on Windows, macOS, Linux, iOS, Android.
  • You also want full webrequest blocking.
Mozilla Firefox review

Questions people ask

Is Fastmail or Mozilla Firefox better?
Neither clearly leads. Fastmail starts at $3/month and Mozilla Firefox at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Fastmail or Mozilla Firefox?
Mozilla Firefox has a free tier; the other does not. Paid plans start at $3/month for Fastmail and Free for Mozilla Firefox.
Does Fastmail or Mozilla Firefox run on more platforms?
Fastmail runs on Web, iOS, Android, macOS, Windows. Mozilla Firefox runs on Windows, macOS, Linux, iOS, Android.
Can I use Mozilla Firefox for free?
Yes. Mozilla Firefox has a free tier, so you can try it without paying. Fastmail starts at $3/month.
What is Fastmail best used for?
Fastmail is most often used for someone who wants their email address tied to a domain they own rather than a free provider they do not, a small business wanting hosted mail on its own domain without running mail server infrastructure, a person leaving gmail specifically to stop an ad-funded provider processing their mail, a household migrating several accounts to one paid provider with shared billing. Of those, someone who wants their email address tied to a domain they own rather than a free provider they do not and a small business wanting hosted mail on its own domain without running mail server infrastructure are not what Mozilla Firefox is typically brought in for.
What can Fastmail do that Mozilla Firefox cannot?
Fastmail covers Custom domain hosting, Masked email, Unlimited aliases, Integrated calendar and contacts. Mozilla Firefox covers Gecko engine, Full webRequest blocking, Total Cookie Protection, Container tabs.

Answered from the vendors’ own pages

Fastmail: Is Fastmail a client like Spark, or does it host my email?

It hosts the mailbox itself; there is no separate provider underneath it the way Spark sits over Gmail.

Mozilla Firefox: Does uBlock Origin still work on Firefox?

Yes. Firefox has kept the blocking webRequest API that Chrome removed with Manifest V3, so uBlock Origin runs with its full rule set rather than the cut-down Lite version Chrome requires.

Fastmail: Does Fastmail offer end-to-end encryption?

Not by default in the way Proton Mail or Tuta do; its privacy position rests on being subscription-funded rather than ad-funded.

Mozilla Firefox: Is Firefox on iPhone the same browser?

No. Apple's platform rules require it to use WebKit, so on iOS and iPadOS you get Firefox's interface, Sync and bookmarks on top of Safari's engine. The privacy and extension behaviour are not the same.

Fastmail: Can I use my own domain?

Yes, from the Standard plan up, with full alias and masked email support.

Mozilla Firefox: How is Mozilla funded, and does that matter?

Mainly by payments for making a search engine the default, with Google as the dominant payer. It matters because it is a single-source dependency on a direct competitor, and it has been the subject of antitrust litigation whose outcome Mozilla does not control.

Mozilla Firefox: Can I manage it across a company fleet?

Yes, through policies.json or Windows Group Policy with the ADMX templates, and the ESR channel gives you a roughly yearly major version instead of four-weekly. There is no first-party cloud management console, so reporting needs other tooling.

Mozilla Firefox: Will every site work in it?

Most will. The exceptions cluster around sites tested only in Chrome, legacy enterprise applications, and anything using WebUSB, WebSerial, Web Bluetooth or WebHID, which Firefox does not implement at all.

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