To automatically discover mail server connection settings upon entering just your email address, clients such as Thunderbird download an XML file at http://autoconfig.emailaddressdomain/mail/config-v1.1.xml?emailaddress=emailaddress¹.

You also need to configure the corresponding DNS entries, usually a CNAME for autoconfig.example.com (where example is the mail TLD after the @)

For Outlook / Office 365 it looks like this:

Service: _autodiscover
Protocol: ._tcp
Port Number: 443
Host: mail.contoso.com

Where mail.contoso.com is your Outlook server namespace.

You also need an XML which looks like this:

http://autoconfig.emailaddressdomain.example.com/mail/config-v1.1.xml?emailaddress=emailaddress

<?xml version="1.0" encoding="UTF-8"?>
<clientConfig version="1.1">
  <emailProvider id="mailbox.org">
    <domain>mailbox.org</domain>
    <displayName>mailbox.org -- damit Privates privat bleibt</displayName>
    <displayShortName>mailbox.org</displayShortName>
    <incomingServer type="imap">
      <hostname>imap.mailbox.org</hostname>
      <port>993</port>
      <socketType>SSL</socketType>
      <authentication>password-cleartext</authentication>
      <username>%EMAILADDRESS%</username>
    </incomingServer>
    <incomingServer type="imap">
      <hostname>imap.mailbox.org</hostname>
      <port>143</port>
      <socketType>STARTTLS</socketType>
      <authentication>password-cleartext</authentication>
      <username>%EMAILADDRESS%</username>
    </incomingServer>
    <incomingServer type="pop3">
      <hostname>pop3.mailbox.org</hostname>
      <port>995</port>
      <socketType>SSL</socketType>
      <authentication>password-cleartext</authentication>
      <username>%EMAILADDRESS%</username>
    </incomingServer>
    <incomingServer type="pop3">
      <hostname>pop3.mailbox.org</hostname>
      <port>110</port>
      <socketType>STARTTLS</socketType>
      <authentication>password-cleartext</authentication>
      <username>%EMAILADDRESS%</username>
    </incomingServer>
    <outgoingServer type="smtp">
      <hostname>smtp.mailbox.org</hostname>
      <port>465</port>
      <socketType>SSL</socketType>
      <authentication>password-cleartext</authentication>
      <username>%EMAILADDRESS%</username>
    </outgoingServer>
    <outgoingServer type="smtp">
      <hostname>smtp.mailbox.org</hostname>
      <port>587</port>
      <socketType>STARTTLS</socketType>
      <authentication>password-cleartext</authentication>
      <username>%EMAILADDRESS%</username>
    </outgoingServer>
    <documentation url="http://www.mailbox.org/">
      <descr lang="de">FAQ und Support-Datenbank</descr>
      <descr lang="en">Frequently Asked Questions (FAQ)</descr>
    </documentation>
  </emailProvider>
</clientConfig>

The autoconfig component configured by iRedMail Easy supports URLs²:

• https://mail.host.com/mail/config-v1.1.xml
• https://mail.host.com/.well-known/autoconfig/mail/config-v1.1.xml
• https://autoconfig.host.com/mail/config-v1.1.xml (DNS A record of autoconfig.host.com must be pointed to IP of your mail server a.b.c.d.)
• https://autoconfig.host.com/.well-known/autoconfig/mail/config-v1.1.xml (DNS A record of autoconfig.host.com must be pointed to IP of your mail server a.b.c.d.)

• How to configure e-mail clients automatically through DNS