This was a bug in earlier cPanel 11 versions and some late cPanel 10.

When viewing mail in SquirrelMail you have the option of clicking the “More” link after the TO address to view all recipients.  When doing so, you receive this error:

ERROR:
ERROR: Could not complete request.
Query: SELECT “”
Reason Given: SELECT failed: Can’t open mailbox : no such mailbox

Fix:

You will need to comment out lines 215, 216, and 217 in /usr/local/cpanel/base/3rdparty/squirrelmail/functions/strings.php

 ;——————————————————————————————-

/**
* php_self
*
* Creates an URL for the page calling this function, using either the PHP global
* REQUEST_URI, or the PHP global PHP_SELF with QUERY_STRING added.
*
* @return string the complete url for this page
*/
function php_self () {
// if ( sqgetGlobalVar(’REQUEST_URI’, $req_uri, SQ_SERVER) && !empty($req_uri) ) {
// return $req_uri;
// }

if ( sqgetGlobalVar(’PHP_SELF’, $php_self, SQ_SERVER) && !empty($php_self) ) {
// need to add query string to end of PHP_SELF to match REQUEST_URI
//
if ( sqgetGlobalVar(’QUERY_STRING’, $query_string, SQ_SERVER) && !empty($query_string) ) {
$php_self .= ‘?’ . $query_string;
}

;——————————————————————————————-