Fastmail vs Mattermost

Fastmail (Open-source software developed at Fastmail.) and Mattermost (Mattermost is a secure collaboration platform for connecting your teams, tools and processes to accelerate mission-critical work.) both appear on the Smoower Developer Ecosystem Index.

Mattermost (rank #38) holds a meaningful lead over Fastmail (rank #430) on the overall Smoower ecosystem score (62 vs 40). The gap of 22 points reflects composite signals across code, docs, community and reach.

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

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. Mattermost shows 49,882 stars across 262 public repos, 58 active in the last 90 days and 105 external contributors. The star gap on its own does not decide the comparison, but Mattermost's footprint is roughly 7.9x larger, which usually shows up in downstream signals like inbound issues and third party integrations.

Fastmail is worth a look for teams already invested in its stack. Mattermost 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.