Hello,
When i try to send emails to an t-mobile address i get a mail return email back saying Recipient address rejected: You are greylisted for 600 seconds
but when reading up on this link it states that if you get a permanent error (which i am) the mail server is not retrying aggressive enough, so i looked in WHM and all the mails to these t-mobile addresses are queuing, how do i stop this? What is the issue?

many thanks
Dan