eml775 B

EML — Exchange-Style Thread-Index Alongside References

A reply carrying the Exchange threading headers — Thread-Topic and a SAMPLE Thread-Index — next to the standard References chain, plus an X-MS header with an empty value. Empty header values are legal and are a common cause of parser exceptions.

Email parsing Conversion testing

Preview — first 18 lineseml

From: Sam Rivera <sam@meridiansupply.example>
To: Maya Chen <maya@brightside.example>
Subject: Re: Standing order for Q1 (SAMPLE)
Date: Sun, 15 Feb 2026 09:00:00 -0800
Message-ID: <p7-thread-index@meridiansupply.example>
In-Reply-To: <p7-thread-002@meridiansupply.example>
References: <p7-thread-root@brightside.example> <p7-thread-002@meridiansupply.example>
Thread-Topic: Standing order for Q1 (SAMPLE)
Thread-Index: AQHcSAMPLEthreadIndexBase64Placeholder0000AAAA==
X-MS-Has-Attach: 
X-MS-Exchange-Organization-SCL: -1
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit

Reply body. What matters here is which threading headers are present
and what they point at; the text is the same across the set on purpose.

Specifications

Wave: p7
Seed: 20260807
Thread Topic: Standing order for Q1 (SAMPLE)
Thread Index Is Sample: true
References: 2
Empty Header Present: X-MS-Has-Attach
Line Endings: CRLF (RFC 5322)

Testing contract

Expected to pass

Scenario: Parse a message that carries both standard and Exchange threading headers, one of which has an empty value.
Expected result: Threading follows References, Thread-Topic and Thread-Index are exposed as ordinary headers, and the empty X-MS-Has-Attach value parses as an empty string rather than raising.

What is a .eml file?

An EML file is a single email message stored in the RFC 822 / MIME format — plain-text headers (From, To, Subject, Date, Message-ID) followed by the body, which may be plain text, HTML, or a multipart structure with alternative bodies and file attachments encoded in base64.

How to use this file

Use an example EML to test email header parsing, MIME decoding, HTML-part handling, attachment extraction, and EML-to-other-format conversion.

How to use this file for testing

“EML — Exchange-Style Thread-Index Alongside References” is a deterministic Novus Examples fixture for Email parsing, Conversion testing. Standards-compliant RFC 822 messages — plain, multipart text+HTML, and with an attachment — plus an MBOX mailbox, for testing header parsing, MIME decoding, attachment extraction, and mailbox splitting.

Documented properties for this file: seed 20260807 · CRLF (RFC 5322). Compare results against paired or grouped companions on this page when present (clean↔damaged, searchable↔scanned, or format twins) so scores stay reproducible across runs.

Download the file once, keep the path stable in CI or local scripts, and treat the spec table as the contract: dimensions, seeds, field lists, and roles are intentional. Corrupt or invalid samples are labelled as such — expect parsers to fail loudly rather than silently accept them.

Email fixtures use fixed dates, message IDs, and MIME boundaries so runs are reproducible, and every address is fictional. Test header parsing, MIME decoding, attachment extraction, and EML/MBOX conversion against the documented structure.

Code examples

from email import policy
from email.parser import BytesParser

msg = BytesParser(policy=policy.default).parse(open("p7-exchange-thread-index.eml", "rb"))
print(msg["subject"], msg["from"])