Mailserver Configuration Discovery

A Java library for looking up published mailserver configurations for clients for a given domain.

Supported discovery methods:

SRV records (RFC 6186)
Mozilla Autoconf

Possibly supported soon:

Microsoft Office Autodiscover v1 (only for http(s) URIs)
Apple Mail Profile Autoconfig

Microsoft Office Autodiscover v2 is not expected to be supported in the future.

Usage

The easiest way to determine mailserver configurations can be done without configuration based on the domain or the whole email address.

List<MailserverService> servicesA = MailserverConfigurationDiscovery.discover( "dummy-domain.com" );
List<MailserverService> servicesB = MailserverConfigurationDiscovery.discover( EmailAddress.of( "user@dummy-domain.com" ) );

Context Configuration

With the help of a context, the query can be configured in many ways. To build a context the MailserverConfigurationDiscoveryContextBuilder is used.

Use only RFC 6186 configurations:

var context = new MailserverConfigurationDiscoveryContextBuilder()
    .withConfigurationMethods( ConfigurationMethod.RFC_61186 )
    .build();
var services = MailserverConfigurationDiscovery.discover( "dummy-domain.com", context );

To only look for submission protocol configurations:

var context = new MailserverConfigurationDiscoveryContextBuilder()
    .withDiscoveryScopes( MailserverConfigurationDiscoveryContext.DiscoveryScope.SUBMISSION )
    .build();
var services = MailserverConfigurationDiscovery.discover( "dummy-domain.com", context );

A custom DNS resolver can also be configured:

var context = new MailserverConfigurationDiscoveryContextBuilder()
    .withDnsServer( "9.9.9.9" )
    .withDnsLookupTimeout( Duration.ofSeconds( 50 ) )
    .withDnsLookupRetries( 5 )
    .build();
var services = MailserverConfigurationDiscovery.discover( "dummy-domain.com", context );

The discovery is run as concurrent task. If you want to use a custom Executor, you can overwrite the default one:

var context = new MailserverConfigurationDiscoveryContextBuilder()
    .withExecutor( new ForkJoinPool( 1 ) )
    .build();
var services = MailserverConfigurationDiscovery.discover( "dummy-domain.com", context );

Discovered Mailserver Configurations

Depending on the method used to discover the configurations, they can be cast into their corresponding types.

var services = MailserverConfigurationDiscovery.discover( "dummy-domain.com" );
for( MailserverService service : services ) {
  if( service instanceof SrvRecordMailserverService srvRecordMailserverService ) {
    // ...
  } else if( service instanceof MozillaAutoconfMailserverService mozillaAutoconfMailserverService ) {
    // ...
  }
}

var services = MailserverConfigurationDiscovery.discover( "dummy-domain.com" );
for( MailserverService service : services ) {
  if( service.getConfigurationMethod() == ConfigurationMethod.RFC_61186 ) {
    var srvRecordMailserverService = (SrvRecordMailserverService) service;
    // ...
  } else if( service.getConfigurationMethod() == ConfigurationMethod.MOZILLA_AUTOCONF ) {
    var mozillaAutoconfMailserverService = (MozillaAutoconfMailserverService) service;
    // ...
  }
}

Changelog

0.1.0

MailserverConfigurationDiscovery returns sets instead of lists now, s.th. result set won't contain duplicates

0.0.3

fix XXE_DOCUMENT and URLCONNECTION_SSRF_FD bugs when looking up XML autoconf files

0.0.2

add support for Mozilla Autoconf
remove synchronous discovery to minimize complexity

0.0.1

initial release with RFC 6186 support

adlange / mailserver-configuration-discovery