SETUP RELAY FOR ONE STALWART SERVER TO ANOTHER

[Machos65]

I Have two different stalwart server in different domain lets say domain A and domain B now i want to domain B to be relay of domain A, now i get error
2025-09-23T16:53:54Z INFO SMTP authentication failed (delivery.auth-failed) queueId = 265009619294749369, queueName = "local", from = "<>", to = ["tst@domainA.com"], size = 3269, total = 1, hostname = "domainB.com", causedBy = SMTP error occurred (smtp.error) { details = "Unsupported Authentication Mechanism" }, elapsed = 0ms
the picture are the config of domain A

what configuration am i missing there