help/content/reference/checkers/email-autoconfig.en.md

date	author	title	description	weight
2026-06-11T09:00:00+02:00	nemunaire	Mail autoconfiguration	Verify that a domain publishes discoverable mail-client configuration through Thunderbird autoconfig, Microsoft Autodiscover and RFC 6186 SRV records.	220

The Mail Autoconfiguration checker verifies that mail clients can automatically discover how to connect to your mail servers. When autoconfiguration is published correctly, a user only types their email address and password, and their client (Thunderbird, Outlook, mobile mail apps…) finds the right IMAP/POP and SMTP hosts, ports and security settings on its own.

This checker is service-level: it applies to the mail-autoconfiguration and RFC 6186 services of a domain. For each run it probes the discovery mechanisms used by real-world clients:

• Thunderbird autoconfig (Bucksch draft): https://autoconfig.<domain>/mail/config-v1.1.xml as the primary URL, with the https://<domain>/.well-known/autoconfig/... apex fallback, an optional plain-HTTP variant, the Mozilla ISPDB fallback, and MX-parent fallbacks.
• Microsoft Autodiscover (POX): https://autodiscover.<domain>/autodiscover/autodiscover.xml.
• RFC 6186 SRV records: _imaps, _imap, _pop3s, _pop3, _submissions, _submission, _autodiscover.
• MX resolution, for context and MX-based discovery.

It parses every response, cross-checks the servers advertised by the different sources, and produces an HTML report with paste-ready remediation snippets for the most common failure modes.

What it checks

Rule	What it verifies	Severity on failure
autoconfig_presence	At least one autoconfiguration discovery method answers for the domain.	Critical
autoconfig_preferred_endpoint	The primary URL https://autoconfig.<domain>/mail/config-v1.1.xml is reachable and serves a valid clientConfig.	Warning
autoconfig_tls	Autoconfig endpoints are served over HTTPS with a valid TLS certificate.	Critical
autoconfig_server_encryption	Servers advertised by autoconfig use SSL or STARTTLS and a non-cleartext authentication method.	Critical
autoconfig_consistency	Hostnames and ports reported by autoconfig, Autodiscover and SRV records agree with each other.	Warning
autoconfig_srv_records	RFC 6186 SRV records complement the autoconfig XML.	Warning
autoconfig_autodiscover	Whether Microsoft Autodiscover (POX) responds on the domain.	Warning

When a check fails, the report's "Fix this first" section provides ready-to-copy snippets: a sample config-v1.1.xml and its canonical URLs when nothing is published, a nudge to add the autoconfig. subdomain when only .well-known answers, an HTTPS redirect hint, a certificate-coverage hint, a port cheat-sheet for plaintext servers (SSL 993/465, STARTTLS 143/587), and a ready-to-paste SRV zone excerpt.

Options

Per user

Option	Meaning	Default
Local-part used in probes (probeEmail)	Local part sent in the autoconfig URL query string (before @). Most servers ignore it.	test
HTTP timeout (httpTimeout)	Per-request timeout, in seconds, when probing endpoints.	8
Try Mozilla ISPDB fallback (tryISPDB)	When the domain publishes no autoconfig file, also query Mozilla's public Thunderbird ISPDB.	true
Allow plain-HTTP fallback probe (tryHTTPAutoconfig)	Also probe the plain-HTTP variant of autoconfig.<domain> (optional in the draft); useful to spot HTTP-only providers.	false
Probe Microsoft Autodiscover (tryAutodiscoverPost)	Probe the Exchange/Outlook Autodiscover endpoints. Disable to check only the Thunderbird flow.	true

Admin

Option	Meaning	Default
Mozilla ISPDB base URL (ispdbURL)	Base URL of Mozilla's autoconfig fallback database.	https://autoconfig.thunderbird.net/v1.1/
User-Agent used in probes (userAgent)	User-Agent announced in every probe request.	happyDomain-autoconfig/1.0 (+https://happydomain.org)

In happyDomain

Enable this checker from the Checks tab of the relevant mail-autoconfiguration service. See {{< relref "/pages/checks" >}} for scheduling and reading checks.

This checker is the natural companion to a full mail setup: see {{< relref "/reference/services/email" >}} for the MX, SPF, DKIM and DMARC services that govern how mail is delivered and authenticated.