出于某种原因，我突然在詹姆斯身上遇到了这个错误：
DEBUG 09:32:35,635 | james.smtpserver | Id='1973954440' User='' Unknown domain ABC so reject it
DEBUG 09:32:35,635 | james.smtpserver | Id='1973954440' User='' executing hook org.apache.james.protocols.smtp.core.log.HookResultLogger@340c2af4
DEBUG 09:32:35,635 | james.smtpserver | Id='1973954440' User='' org.apache.james.smtpserver.fastfail.ValidRcptHandler: result=8 (DECLINED)
任何线索有效域被拒绝有什么问题？