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Productivity · head to head

Fastmail vs Microsoft 365

Fastmail logo

Fastmail

Productivity

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

From
$3/month
Rated
-
Full reviewWebsite
Microsoft 365 logo

Microsoft 365

Productivity

Subscription bundle of the Office applications with mail, storage, meetings and organisational identity

From
$7/month
Rated
-
Full reviewWebsite

The short version

  • 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.; Microsoft 365 business plans are capped at 300 seats, so an organisation that grows past that must move to Enterprise plans, which changes both the price per user and the feature mix at the moment it can least afford a migration project.
  • They diverge on capability: Fastmail covers Custom domain hosting, Microsoft 365 covers Office applications.
  • Prices and features above were last checked on 1 September 2026.

Where they differ

Only the attributes on which Fastmail and Microsoft 365 actually diverge.

Attributes where Fastmail and Microsoft 365 differ
AttributeFastmailMicrosoft 365
Starting price$3/month$7/month
Pricing modelPer user per monthsubscription
PlatformsWeb, iOS, Android, macOS, WindowsWeb

Identical on both: free tier (No), user rating (Not yet rated), category (Productivity).

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 Microsoft 365

  • Office applications
  • Hosted services
  • Teams
  • Microsoft Entra ID
  • OneDrive storage
  • Device management and endpoint protection
  • Purview compliance
  • Copilot

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 Microsoft 365
  • A small business wanting hosted mail on its own domain without running mail server infrastructurenot Microsoft 365
  • A person leaving Gmail specifically to stop an ad-funded provider processing their mailnot Microsoft 365
  • A household migrating several accounts to one paid provider with shared billingnot Microsoft 365

Microsoft 365

  • Any organisation that wants mail, documents, meetings and identity from one supplier on one bill.not Fastmail
  • A company standardising on single sign-on, where Entra ID becomes the account other services authenticate against.not Fastmail
  • Regulated work that needs retention, legal hold and eDiscovery across mail and documents, provided the tier that includes them is actually bought.not Fastmail
  • A household that needs installed Office applications on several machines rather than browser-only editing.not 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.

Microsoft 365

  • Business plans are capped at 300 seats, so an organisation that grows past that must move to Enterprise plans, which changes both the price per user and the feature mix at the moment it can least afford a migration project.
  • The compliance capabilities most organisations eventually need, including retention, data loss prevention, advanced eDiscovery and insider risk, sit at the top tier or in add-ons, so the real cost surfaces after an audit or a customer questionnaire rather than at purchase.
  • Annual term subscriptions commit you for the year and month-to-month terms cost measurably more per seat, so the flexibility to reduce seats during a quiet period is bought at a permanently higher rate.
  • Entra ID becomes the identity for everything else the organisation uses, which is the hardest kind of lock-in to put a number on, because leaving means re-federating every connected application rather than simply replacing a word processor.
  • The licensing model is complicated enough that most organisations are either over-licensed or quietly non-compliant, and reconciling it usually requires a partner or a specialist, which is a recurring cost that never appears in the advertised per-user figure.

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

Microsoft 365

$7/month
  • Microsoft 365 Business Basic$7/month
    • Email and calendar with 50 GB mailbox
    • Web and mobile versions of Office apps
    • Microsoft Teams included
  • Microsoft 365 Business Standard$14/month
    • Desktop versions of Word, Excel, PowerPoint, Outlook
    • Email and Teams
    • 1 TB cloud storage per user
  • Microsoft 365 E5$60/month
    • Comprehensive security and compliance
    • All productivity apps
    • Advanced analytics

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 Microsoft 365 if

  • You need office applications.
  • You also want hosted services.
Microsoft 365 review

Questions people ask

Is Fastmail or Microsoft 365 better?
Neither clearly leads. Fastmail starts at $3/month and Microsoft 365 at $7/month, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Fastmail or Microsoft 365?
Fastmail starts at $3/month and Microsoft 365 at $7/month.
Does Fastmail or Microsoft 365 run on more platforms?
Fastmail runs on Web, iOS, Android, macOS, Windows. Microsoft 365 runs on Web.
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 Microsoft 365 is typically brought in for.
What can Fastmail do that Microsoft 365 cannot?
Fastmail covers Custom domain hosting, Masked email, Unlimited aliases, Integrated calendar and contacts. Microsoft 365 covers Office applications, Hosted services, Teams, Microsoft Entra ID.

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.

Microsoft 365: What is the difference between Microsoft 365 and Office?

Office was a one-off licence for a specific version. Microsoft 365 is a subscription covering the applications and the hosted services together, and when payment stops the applications drop to a reduced state rather than continuing as they were.

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.

Microsoft 365: Is Teams included?

Not automatically for newer customers. Microsoft unbundled Teams and now sells it alongside the suite, so check what a given quotation actually covers.

Fastmail: Can I use my own domain?

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

Microsoft 365: What happens to our files if we stop paying?

The documents remain yours and can be downloaded, but access to hosted mailboxes and sites ends after a retention window, so leaving requires a planned export rather than a cancellation.

Microsoft 365: Is Copilot part of the subscription?

No. It is a per-user add-on on top of the base licence, generally with its own term commitment, and it is priced per seat regardless of how much any individual uses it.

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