check-sieve(1)

💅 check-sieve(1) — General Commands Manual, but make it group chat 💅

okay so bestie, this is the manual for check-sieve: the syntax checker for mail sieves. it lives in the General Commands Manual, it has a whole lot of RFC energy, and we're gonna get into all of it. no cap. 🫶

🌸 NAME 🌸

check-sieve — syntax checker for mail sieves. periodt. 💖

✨ SYNOPSIS ✨

here's the shape of it, bestie:

check-sieve [options] file [ file ...  ]
check-sieve --help
check-sieve --version

🦋 DESCRIPTION 🦋

okay so check-sieve is a simple syntax checker for server-side mail sieves. it supports many mail-sieve RFCs, and the details are literally below. iykyk. 🌈

🎀 OPTIONS 🎀

• -h, --help — show the program help.
• --max-list-length N — check the length of string lists, and flag any that are longer than the specified length.
• --server <host>:<port> — connect to the specified server, and only enable advertised capabilities.
• --trace-parser — trace the operation of the parser.
• --trace-scanner — trace the operation of the scanner.
• --trace-tree — trace the abstract-syntax-tree.
• --simulate <email-file> — simulate sieve processing against an email file (.eml format). see SIMULATION below.
• --test-dir <dir> — run simulation for every .eml file in dir and diff each result against a matching .out file. see SIMULATION below.
• --rebase <dir> — regenerate the .out files in dir from current simulation output. see SIMULATION below.
• --version — print out version information.

🧪 SIMULATION 🧪

check-sieve can simulate how a sieve script sorts mail, making it straightforward to verify script behavior without deploying to a mail server. so you can test the vibe before it hits prod. 💅

💌 Single-message simulation 💌

• --simulate <email-file> — validates the sieve script and then evaluates it against the given .eml file. each test that matches is printed as MATCH: <test> and each executed action as ACTION: <action>. if no delivery action is taken, keep (implicit) is added automatically per RFC 5228 §4.2.

NOTE: Many RFC extensions are still in progress. Filing an issue for unsupported extensions will help prioritize what to work on next. 🫶

🧺 Batch testing with a test directory 🧺

A test directory contains .eml files and, optionally, .out files that record expected simulation output. the .out file for a given email is named after the email's stem (e.g. msg.eml → msg.out).

• --test-dir <dir> — runs simulation against every .eml file in dir. for each email that has a matching .out file, the actual output (with the environment-specific first line stripped) is diffed against it. if all comparisons pass the program exits 0 with no output. if any differ, each diff is printed followed by a summary on stderr and the program exits 1. emails without a .out file are simulated but not compared.
• --rebase <dir> — regenerates the .out file for every .eml file in dir, creating or overwriting as needed. run this after making intentional changes to a sieve script or the simulator to update the expected output before re-running --test-dir.

🐛 BUGS 🐛

for information on existing issues, and to file a bug report check the following URL: https://github.com/dburkart/check-sieve/issues

👑 AUTHORS 👑

• Dana Burkart
• Stuart Montgomery

🌈 SUPPORTED RFCs 🌈

the full list of supported RFCs is:

• Sieve: An Email Filtering Language (RFC 5228)
• Variables Extension (RFC 5229)
• Date and Index Extensions (RFC 5260)
• Vacation Extension (RFC 5230)
• Vacation "Seconds" Parameter (RFC 6131)
• Include Extension (RFC 6609)
• Copying Without Side Effects (RFC 3894)
• Reject and Extended Reject Extensions (RFC 5429)
• Body Extension (RFC 5173)
• Relational Extension (RFC 5231)
• MIME Part Tests, Iteration, Extraction, Replacement, and Enclosure (RFC 5703)
• Imap4flags Extension (RFC 5232)
• Editheader Extension (RFC 5293)
• Regex Extension (DRAFT)
• Spamtest and Virustest Extensions (RFC 5235)
• Extensions for Notifications (RFC 5435)
• Subaddress Extension (RFC 5233)
• Ihave Extension (RFC 5463)
• Environment Extension (RFC 5183)
• Sieve Notification Mechanism: mailto (RFC 5436)
• Internet Message Access Protocol (IMAP) Events (RFC 6785)
• Converting Messages before Delivery (RFC 6558)
• Detecting Duplicate Deliveries (RFC 7352)
• Externally Stored Lists (RFC 6134)
• Delivering to Special-Use Mailboxes (RFC 8579)
• File Carbon Copy (FCC) (RFC 8580)
• Delivery by MAILBOXID (RFC 9042)
• Delivery Status Notifications and Deliver-By Extensions (RFC 6009)
• Extension for Processing Calendar Attachments (RFC 9671)
• Proton Expiration Extension (vendor-specific)
• Proton Eval Extension (vendor-specific)
• Dovecot Invoking External Programs (vendor-specific)

mwah 💋 — this page is from version 1.0.1, dated 10 Apr 2026, and it's the check-sieve(1) page. byeee bestie 🫶