Mailcow vs Stalwart vs Mailu at 10,000 Mailboxes: What Holds Up in Production
Most "mailcow vs Stalwart vs Mailu" posts are written from a homelab: one domain, a handful of mailboxes, a feature checklist. That's a fine way to pick a server for your family. It tells you very little about what happens at 10,000 mailboxes, where the questions change from "does it have a spam filter" to "what happens when one node dies" and "how do I provision ten thousand accounts without…
Three email server solutions - Mailcow, Stalwart, and Mailu - were evaluated based on their performance at 10,000 mailboxes. This article focuses on the production data collected for Stalwart, while Mailcow and Mailu were assessed through their official documentation.
Mailcow is a comprehensive solution, featuring webmail, calendars, contacts, and Exchange ActiveSync. It requires a minimum of 6 GiB of RAM plus 1 GiB of swap, with additional memory needed for ClamAV and full-text search. The system uses Docker Compose and includes SOGo for webmail, calendars, contacts, and ActiveSync. Mailbox migration is facilitated by sync jobs, and the community offers extensive support.
However, Mailcow is a single host solution, with no documented active-active or multi-node mode. In a production scenario, restoring to a standby machine could result in scheduled outages.
Stalwart is a single Rust binary that handles all mail and groupware protocols itself. It offers JMAP support for better webmail performance and external storage integration. Stalwart keeps metadata in PostgreSQL and message blobs in S3-compatible object storage, enabling scalable storage and easy backup. The system requires setting up PostgreSQL, configuring MinIO, and adjusting the storage class for ReadWriteMany access in Kubernetes.
While Stalwart provides more robust scalability, it necessitates a more complex setup and management.
Mailu, on the other hand, is lightweight and compatible with Kubernetes, with Helm chart support. Its requirements are minimal: 1 GB of RAM and 1 GB of swap without antivirus, rising to 3 GB with ClamAV. Webmail options include Roundcube or SnappyMail, and the system offers a REST API for administration. However, Mailu's storage setup using ReadWriteMany access could pose challenges for high-availability configurations.
Overall, each solution offers unique advantages and trade-offs, depending on the specific needs and resources of the deployment.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
