Hostname validation errors: 1 Message(s), 211 Time(s)

**Unmatched Entries**

910F61DE067C: host mx2a.comcast.net[76.96.30.116] refused to talk to me: 554 imta20.emeryville.ca.mail.comcast.net comcast 220.241.233.244 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://help.comcast.net/content/faq/PTR
4CA251DE069C: host mx1.comcast.net[76.96.62.116] refused to talk to me: 554 imta17.westchester.pa.mail.comcast.net comcast 220.241.233.244 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://help.comcast.net/content/faq/PTR
C364F1DE0688: host mx1a.comcast.net[76.96.62.116] refused to talk to me: 554 imta17.westchester.pa.mail.comcast.net comcast 220.241.233.244 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://help.comcast.net/content/faq/PTR
12E2A1DE0689: host mx1.comcast.net[76.96.62.116] refused to talk to me: 554 imta17.westchester.pa.mail.comcast.net comcast 220.241.233.244 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://help.comcast.net/content/faq/PTR
A05FC1DE066C: host mx1b.comcast.net[76.96.62.116] refused to talk to me: 554 imta17.westchester.pa.mail.comcast.net comcast 220.241.233.244 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://help.comcast.net/content/faq/PTR
4CA251DE069C: host mx2.comcast.net[76.96.30.116] refused to talk to me: 554 imta20.emeryville.ca.mail.comcast.net comcast 220.241.233.244 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://help.comcast.net/content/faq/PTR
12E2A1DE0689: host mx2b.comcast.net[76.96.30.116] refused to talk to me: 554 imta20.emeryville.ca.mail.comcast.net comcast 220.241.233.244 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://help.comcast.net/content/faq/PTR
A05FC1DE066C: host mx2a.comcast.net[76.96.30.116] refused to talk to me: 554 imta20.emeryville.ca.mail.comcast.net comcast 220.241.233.244 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://help.comcast.net/content/faq/PTR
910F61DE067C: host mx1a.comcast.net[76.96.62.116] refused to talk to me: 554 imta17.westchester.pa.mail.comcast.net comcast 220.241.233.244 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://help.comcast.net/content/faq/PTR
C364F1DE0688: host mx1b.comcast.net[76.96.62.116] refused to talk to me: 554 imta17.westchester.pa.mail.comcast.net comcast 220.241.233.244 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://help.comcast.net/content/faq/PTR
12E2A1DE0689: host mx2a.comcast.net[76.96.30.116] refused to talk to me: 554 imta20.emeryville.ca.mail.comcast.net comcast 220.241.233.244 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://help.comcast.net/content/faq/PTR
A05FC1DE066C: host mx2b.comcast.net[76.96.30.116] refused to talk to me: 554 imta20.emeryville.ca.mail.comcast.net comcast 220.241.233.244 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://help.comcast.net/content/faq/PTR
910F61DE067C: host mx2b.comcast.net[76.96.30.116] refused to talk to me: 554 imta20.emeryville.ca.mail.comcast.net comcast 220.241.233.244 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: http://help.comcast.net/content/faq/PTR

各位老大这个提示是那里出问题了，需要怎么样解决呀。最近的邮件有很多这样的提示，不知道怎么样解决，谢谢！