Hi there,
Sorry my suggested change was not complete.
Please edit again the file /common/toolbox.php and replace line 574 . . .
$html = preg_replace_callback($rxEML,function ($m) { global $tit, $sda, $xx; return "{$m[1]}<a class='link' href='mailto:{$m[2]}@{$m[3]}.{$m[4]}?subject=$sda%20-%20".str_replace(' ','%20',$tit)."'>".($m[5] ?? $xx['vws_send_mail'])."</a>{$m[6]}"; },$html);
. . .by . . .
$html = preg_replace_callback($rxEML,function ($m) { global $tit, $sda, $xx; return "{$m[1]}<a class='link' href='mailto:{$m[2]}@{$m[3]}.{$m[4]}?subject=$sda%20-%20".str_replace(' ','%20',$tit)."'>".($m[5] ?: $xx['vws_send_mail'])."</a>{$m[6]}"; },$html);
Or, which is much simpler., just replace the ?? before $xx['vws_send_mail'] by ?:
This will solve the problem.
Roel