Support for loading avatars via BIMI

Feature Request

I like to request to add BIMI support for loading avatars in Nextcloud mail. Currently its supported to load the avatars either from an image in the address book, from the favicon of the website or via Gravatar. Adding support for BIMI (partial or complete) is easy, because we only have to check the DNS entries of the corresponding domain and search for the BIMI entry. There we can read the location of the avatar image.

We don't need to implement VMC or DMARC, but we could. Maybe as an option that we can enable/disable if needed.

Example code

Code could look something like this:

function get_bimi_record() {
  $records = dns_get_record( $domain, DNS_TXT );

  foreach ( $records as $record ) {
    if ( strpos( $record['txt'], 'v=BIMI1;' ) === 0 ) {
      return $record['txt'];
    }
  }

  return null;
}

function get_dns_tags( $value ) {
  $tags = explode( ';', $entry );
  $params = [];

  foreach ( $tags as $tag ) {
    list( $name, $value ) = explode( '=', $tag, 2 );
    $name = trim( $name );

    if ( $value ) {
      $params[ $name ] = trim( $value );
    }
  }

  return $params;
}

$dns_record = get_bimi_record();

if ( $dns_record ) {
  $tags = get_dns_tags( $dns_record );
  return $tags['l']; // there is the location
}

Is this feature wanted?

I would create a pull request for this feature request; the question is: do you want it?

References

• https://www.ietf.org/archive/id/draft-blank-ietf-bimi-02.txt

No repository file or test is named. Start by locating the existing avatar-loading entry point and reviewing the referenced BIMI draft alongside the current address-book, favicon, and Gravatar paths; done means the BIMI lookup behavior and its handling of the DNS image location are decided and covered.