sendmail出现以下信息。请高手帮帮忙

sunnytian

There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.
请问是什么错误？怎么解决

sunnytian

There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.

            < xxxxxxx.com #5.5.0>
The e-mail system was unable to deliver the message, but did not report a specific reason.  Check the address and try again.  If it still fails, contact your system administrator.

            < xxxxx #5.0.0 SMTP; 554 too many hops, this message is looping>
基本上是这两种错误