diff --git a/config/example-config.php b/config/example-config.php
index 460ef0c4..82e3673e 100644
--- a/config/example-config.php
+++ b/config/example-config.php
@@ -211,6 +211,13 @@ $c->admin_email ='calendar-admin@example.com';
 */
 // $c->external_refresh = 60;
 
+/**
+* External subscription (BIND) user agent string
+* Required if your remote calendar only delivers to known user agents.
+* Default: none
+*/
+// $c->external_ua_string = '';
+
 /**
 * If you want to force DAViCal to use HTTP Digest Authentication for CalDAV
 * access. Note that this requires all user passwords to be stored in plain text
diff --git a/inc/external-fetch.php b/inc/external-fetch.php
index dd5cddd9..a65e6e02 100644
--- a/inc/external-fetch.php
+++ b/inc/external-fetch.php
@@ -39,7 +39,7 @@ function create_external ( $path,$is_calendar,$is_addressbook )
   }
 }
 
-function fetch_external ( $bind_id, $min_age = '1 hour' )
+function fetch_external ( $bind_id, $min_age = '1 hour', $ua_string )
 {
   if ( ! function_exists ( "curl_init" ) ) {
     dbg_error_log("external", "external resource cannot be fetched without curl, please install curl");
@@ -64,6 +64,8 @@ function fetch_external ( $bind_id, $min_age = '1 hour' )
       curl_setopt ( $curl, CURLOPT_NOBODY, true );
       curl_setopt ( $curl, CURLOPT_TIMEVALUE, $local_ts->format("U") );
       curl_setopt ( $curl, CURLOPT_TIMECONDITION, CURL_TIMECOND_IFMODSINCE );
+      if ( isset( $ua_string ) )
+	  curl_setopt($curl, CURLOPT_USERAGENT, $ua_string);
       dbg_error_log("external", "checking external resource for remote changes " . $row->external_url );
       $ics = curl_exec ( $curl );
       $info = curl_getinfo ( $curl );
@@ -115,7 +117,7 @@ function update_external ( $request )
   if ( $qry->Exec('DAVResource') && $qry->rows() > 0 && $row = $qry->Fetch() ) {
     if ( $row->bind_id != 0 ) {
       dbg_error_log("external", "external resource needs updating, this might take a minute : %s", $row->url );
-      fetch_external ( $row->bind_id, $c->external_refresh . ' minutes' );
+      fetch_external ( $row->bind_id, $c->external_refresh . ' minutes', $c->external_ua_string );
     }
   }
 }