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In Horde3 with IMP4, the IMAP server configuration in imp/config/servers.php had a 'realm' parameter:

<pre><code class="language-php">
\$servers['imap'] = array(
    'name' => 'IMAP Server',
    'server' => 'imap.example.com',
    'hordeauth' => false,
    'protocol' => 'imap/notls',
    'port' => 143,
    'maildomain' => 'example.com',
    'smtphost' => 'smtp.example.com',
    'smtpport' => 25,
    'realm' => 'example.com',
    'preferred' => '',
);
</code></pre>
The purpose of the realm parameter is to append a realm/domain to the Horde username after login.  For example, a user that logged into the server 'imap' from above with a username 'john' would have their Horde username set to '<a href="https://wiki.horde.org/mailto:john@example.com">john@example.com</a>'.  This is useful if you are supporting multiple IMAP servers with a single Horde installation and the usernames in each IMAP server may overlap ('john' at server1 and 'john' at server2 are not the same person).

Horde4 with IMP5 does not have a native 'realm' parameter in imp/config/backends.local.php, but you can replicate the same functionality by modifying the horde 'authusername' hook.  In horde/config/hooks.php:

<pre><code class="language-php">
public function authusername(\$userId, \$toHorde)
\{
    if (\$toHorde) \{
        // Get the IMAP connection object
        \$imap = \$GLOBALS['injector']->getInstance('IMP\_Factory\_Imap')->create();
        // Get the IMAP hostname
        \$hostspec = \$imap->ob->getParam('hostspec');
        // Load the backends.local.php server configs
        \$servers = IMP\_Imap::loadServerConfig();
        // Look through each server for a hostname match
        foreach (\$servers as \$server) \{
            if (\$server['hostspec'] == \$hostspec) \{
                // Append the 'realm' parameter
                \$userId = \$userId . '@' . \$server['realm'];
                break;
            \}
        \}
        return \$userId;
    \} else \{
        // strip the domain off
        \$userId = substr(\$userId, 0, strpos(\$userId, '@'));
        return \$userId;
    \}
\}
</code></pre>
Here is an example IMAP server config from imp/config/backends.local.php:

<pre><code class="language-php">
\$servers['imap'] = array(
    // ENABLED by default
    'disabled' => false,
    'name' => 'IMAP Server',
    'hostspec' => 'localhost',
    'hordeauth' => false,
    'protocol' => 'imap',
    'port' => 143,
    'secure' => 'tls',
    'maildomain' => 'example.com',
    'cache' => false,
    'realm' => 'example.com',
);
</code></pre>
Note the non-standard 'realm' parameter which is used by the authusername hook later.

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