Fastmail vs Microsoft 365

Microsoft 365 is used by more websites in our catalog: 1,580 use Fastmail and 159,483 use Microsoft 365.

Fastmail sites have the higher median Ahrefs Domain Rating (Fastmail: 38, Microsoft 365: 34).

Between 2026-06 and 2026-07, Fastmail went from 0.22% to 0.18% of all tracked sites, while Microsoft 365 went from 21% to 18%. Fastmail is gaining ground faster in our index.

No. A site runs a single email host, so Fastmail and Microsoft 365 are mutually exclusive.

Adoption is counted from Site Stats Database's own crawl; Domain Rating comes from Ahrefs and traffic from DataForSEO. Figures reflect the sites we track and refresh at least monthly.