Fastmail vs office365.us

Fastmail is used by more websites in our catalog: 1,580 use Fastmail and 119 use office365.us.

office365.us sites have the higher median Ahrefs Domain Rating (Fastmail: 38, office365.us: 50).

Between 2026-06 and 2026-07, Fastmail went from 0.22% to 0.18% of all tracked sites, while office365.us went from 0.02% to 0.01%. office365.us is gaining ground faster in our index.

No. A site runs a single email host, so Fastmail and office365.us 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.