PHP Mail BCC recpients被忽略

I am struggling this BCC. I have 2 email addresses that I've included in the BCC field, but only the first email in the field gets the message, the second email is ignored.

i don't know what am doing wrong.

my code is below

$EmailListHere = 'mail1@domain.com,mail2@domain.com';
$headers  = "From: ".$_POST['from-address']."
X-Mailer: php
";
$headers .= "MIME-Version: 1.0
"; #Define MIME Version
$headers .= "Content-Type: text/html; charset=ISO-8859-1
"; #Set content type
$headers .= "Bcc: $EmailListHere
"; #Your BCC Mail List

echo mail(null, $subject=$_POST['subject'], $message=$_POST['html-body'], $headers);