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Stalwart Labs ships mail server 1.0, publishes Postfix/Dovecot tests
Stalwart Labs on Monday released Stalwart v1.0, a Rust mail and collaboration server, and said internal Azure tests found it faster than Postfix 3.11 and Dovecot 2.4 on most headline comparisons.
- New headline Was: “Stalwart v1.0: The Fastest Mail Server on the Planet”
- Our desk filed its story
- stalw.art is now reporting this
Primary sources: Stalwart v1.0 announcement, GitHub releases
Stalwart Labs on Monday released Stalwart v1.0, calling it the first stable version of its open-source mail and collaboration server after five years of work that began with a Rust email parser on Oct. 3, 20211.
The company said the 1.0 line was aimed at performance and a frozen database schema so later upgrades would not require disruptive migrations, and that the server already covers JMAP, IMAP, POP3, SMTP, CalDAV, CardDAV, WebDAV, spam filtering and several storage backends1.
Stalwart said months of profiling produced about 200 commits across more than 1,300 files, with mail-parser 1.0 and a new encoding library, encodify, using SIMD and SWAR to scan headers, MIME boundaries and encodings1. It said the rewritten parser was faster than several other libraries in its own tests, including Dovecot's parser1.
Storage changes described in the post include assigning identifiers inside the same write transaction, zstd dictionaries for mail data, per-backend tuning, and an in-memory message-index cache for IMAP work1. A rewritten full-text search engine stores word positions and, the company said, returned a body search on 250,000 messages in under 4 milliseconds in its lab1.
The firm said it built an Azure stress-test lab spanning more than 30 regions, with 35 kinds of tests and more than 550 cells covering protocols, stores, large mailboxes, connection storms and six-hour soak runs1. It said two rounds of that work found and fixed 97 problems, including a case in which the process held up to 9.6 GB while the heap was under 0.4 GB1.
Head-to-head tests against Postfix 3.11 for SMTP and Dovecot 2.4 for IMAP used identical Azure servers with 8 AMD EPYC Zen 5 vCPUs, 32 GiB of RAM and local NVMe, the company said1. Stalwart said it was faster in 35 of 38 headline comparisons, with IMAP login at 5.1 milliseconds versus 28 milliseconds on Dovecot, inbound SMTP at 5,445 messages per second versus 723 on Postfix, and three Dovecot wins on marking every message in a mailbox as read1.
Those figures are Stalwart's own measurements; the post did not include independent lab results1. The company posted scripts, configurations and raw output to a public GitHub benchmarks repository and listed caveats such as disk-sync differences1.
Other 1.0 features listed include indexing text inside PDF and office attachments, JMAP and IMAP metadata, post-quantum DKIM2 signatures, OAuth changes, and an AI spam classifier in an enterprise edition1. Existing installs must migrate: a 1.0 server will not open an older store1. Clusters now require Redis for the in-memory coordinator, and OAuth follows a public-client profile that some identity providers do not yet support, the company said1.