Mail from old server goes to old server, not to new!

I have 2 servers: Old one Debian6 and new one Debian9, both have virtualmin.
Old server have 2 domains aaa.com and bbb.com
I moved bbb.com to new server and disabled it on old server (not removed). Made changes on hosting provider.
Now when I send e-mail to xxx@bbb.com from gmail or yahoo or other it coming to new server as need. But if send e-mail to xxx@bbb.com from old server domain xxx@aaa.com to xxx@bbb.com it still coming to old server.

Where and what I need to configure to let old server know he must send to new server???

Thank you in advance!