Mail delivery stuck with cPanel

I had an account on one of my servers (cPanel 8) that I relocated to another server (cPanel 8) and now when the old server tries sending mail to the transferred domain it gives this error:

R=lookuphost defer (-1): host lookup did not complete

Any suggestions on how to get it so the old server can send mail to the new server for the domain?

 

 

 

 

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