Store password placeholder as plain text in the database to work around bug, see https://github.com/mail-in-a-box/mailinabox/pull/2305#issuecomment-1767375035

setup/webmail.sh

@@ -154,6 +154,7 @@ cat > ${RCM_PLUGIN_DIR}/carddav/config.inc.php <<EOF;
 /* Do not edit. Written by Mail-in-a-Box. Regenerated on updates. */
 \$prefs['_GLOBAL']['hide_preferences'] = true;
 \$prefs['_GLOBAL']['suppress_version_warning'] = true;
+\$prefs['_GLOBAL']['pwstore_scheme'] = 'plain';
 \$prefs['ownCloud'] = array(
 	'name'         =>  'ownCloud',
 	'username'     =>  '%u', // login username