邮件接收器中继访问被拒绝

[Architect]

是否有人知道“中继访问被拒绝”错误的原因？

Mail-receiver relay access denied

Have this same error with mail-receiver reports: Relay access denied (in reply to RCPT TO command). Mail receiving isn’t working for new install but have got this to work before. Believe all settings are correct but might have missed something.