Fastmail vs Kustomer

Fastmail (Open-source software developed at Fastmail.) and Kustomer both appear on the Smoower Developer Ecosystem Index.

Fastmail (rank #430) holds a narrow lead over Kustomer (rank #602) on the overall Smoower ecosystem score (40 vs 34). The gap of 6 points reflects composite signals across code, docs, community and reach.

On code quality (the state of repositories, tests, releases and polish), Kustomer is ahead of Fastmail. On education (docs, guides and learning material for developers), Fastmail is slightly ahead of Kustomer. On community (issue response, PR reviews and discussion health), Fastmail is ahead of Kustomer. On reach (how visible the ecosystem is beyond its own repos), Fastmail is clearly ahead of Kustomer. On momentum (release cadence and how fast the ecosystem moves), Fastmail is clearly ahead of Kustomer.

Fastmail carries 6,316 GitHub stars across 38 public repos, with 12 repositories active in the last 90 days and 2 external contributors on record. Kustomer shows 15 stars across 19 public repos, 6 active in the last 90 days and 4 external contributors. The star gap on its own does not decide the comparison, but Fastmail's footprint is roughly 421.1x larger, which usually shows up in downstream signals like inbound issues and third party integrations.

Fastmail is the stronger read for anyone weighting reach. Kustomer looks better where code quality is the deciding factor. The table below breaks the scores down pillar by pillar; the linked profiles cover the underlying repos, docs and community signals in full.