Self-hosted apps that integrate with SMTP servers

5 open-source, self-hostable projects list SMTP servers as an integration.

• hook0Self-hosted open-source webhook server with dashboard, HMAC signatures, retries, and delivery monitoring — alternative to Svix and Hookdeck.
• rskyrsky is a full Rust implementation of the AT Protocol letting communities run their own PDS, relays, feed generators, and moderation tools. Open-source under Apache-2.0.
• flowctlflowctl is an open-source self-hosted workflow automation platform for teams to define complex workflows as YAML/HUML files with inputs, approvals, and scheduling.
• surmaiSelf-hosted, open-source travel organizer for personal and family use with collaborative trip planning, offline access, privacy focus, and PWA mobile support.
• LetterSpaceSelf-hosted open-source newsletter tool for managing subscribers, sending campaigns, tracking analytics, and integrating via REST API with full data control.