why can't i receive inbox on mail server

Why can't I receive inbox on the mail server? Even though the status has all green ticks?
i can send email but can't receive email inbox

Hello, I cannot see the specific problem. It is recommended that you check the logs.
Can you send mail from the mail server?

this is the log klik

Hamka
User doesn't exist: postmaster@xxxx.com (in reply to RCPT TO command))