Mail Autodiscovery

AdminBolt configures mail autodiscovery automatically for every domain and subdomain that has email, so mail clients (Microsoft Outlook, Mozilla Thunderbird, Apple Mail, and others) can find the correct server settings on their own. Users only type their email address and password; the client fills in the servers, ports, and security for them.

This is automatic. There is no toggle to enable it and no manual setup: the records and endpoints are published when the domain is created, and kept in sync as things change.

What gets published per domain

When a domain (or subdomain) with mail is created, AdminBolt publishes a set of DNS records. You can see them in the domain's zone (see DNS Templates for the template they come from, and the client Zone Editor for a live zone).

Record	Name	Points to	Purpose
SRV	_imaps._tcp (port 993)	mail host	IMAP over SSL (RFC 6186)
SRV	_pop3s._tcp (port 995)	mail host	POP3 over SSL (RFC 6186)
SRV	_submission._tcp (port 587)	mail host	SMTP submission over STARTTLS (RFC 6186)
SRV	_submissions._tcp (port 465)	mail host	SMTP over SSL (RFC 6186)
SRV	_autodiscover._tcp (port 443)	autodiscover.<domain>	Microsoft Outlook discovery
SRV	_autoconfig._tcp (port 443)	autoconfig.<domain>	Mozilla Thunderbird discovery
A	mail	server IP	Hostname mail clients connect to
A	autoconfig	server IP	Serves the Mozilla autoconfig file
A	autodiscover	server IP	Serves the Outlook autodiscover file
MX	@	mail host	Where mail for the domain is delivered

The mail host is either mail.<domain> or the shared server hostname, depending on whether a per-domain certificate is in place - see Mail host: per-domain or shared below.

How clients discover the settings

On top of the DNS records, AdminBolt serves the per-client autoconfiguration files over HTTPS:

• Microsoft Outlook queries https://autodiscover.<domain>/autodiscover/autodiscover.xml (with the JSON variants .../autodiscover.json?Protocol=Imap and ?Protocol=Smtp for newer clients).
• Mozilla Thunderbird and compatible clients query https://autoconfig.<domain>/.well-known/autoconfig/mail/config-v1.1.xml.
• Clients that follow RFC 6186 read the _imaps, _pop3s, _submission, and _submissions SRV records directly.

The mail.<domain>, autoconfig.<domain>, and autodiscover.<domain> names are all served by the same server and are covered by the domain's certificate (see Mail SNI).

Resulting mail-client settings

Whichever path a client uses, it ends up with the same settings:

Service	Host	Port	Security
IMAP	mail host	993	SSL/TLS
POP3	mail host	995	SSL/TLS
SMTP (submission)	mail host	587	STARTTLS
SMTP (alternative)	mail host	465	SSL/TLS

The username is the full email address (for example [email protected]), and the password is the mailbox password set in Email Accounts.

Mail host: per-domain or shared

The mail host advertised by autodiscovery follows the domain's certificate state:

• No valid per-domain certificate yet - autodiscovery points clients at the shared server hostname. Mail still works; the connection just uses the server's own hostname.
• A valid certificate covering mail.<domain> is in place - autodiscovery, the SRV records, and the MX record switch to mail.<domain>, so each domain has its own mail hostname and certificate. This is handled by Mail SNI.

The switch is automatic in both directions: issuing the certificate moves a domain to mail.<domain>, and removing it falls back to the shared hostname.

Automatic maintenance

• Records and autoconfig files are created when the domain is added.
• They are refreshed automatically when the server hostname changes or when a domain gains or loses its per-domain mail certificate.
• Autodiscovery is enabled by default for Domain and Subdomain types (not for parked domains).

Related

• Mail SNI - per-domain mail certificates over SNI
• Email Settings - the mail backend (Dovecot/Postfix) configuration
• DNS Templates - the template the mail records come from