郵件內容：This is the mail system at host ublink.org. I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below. For further assistance, please send mail to postmaster. If you do so, please include this problem report. You can delete your own text from the attached returned message.The mail system: host mta7.am0.yahoodns.net said:550 5.7.25 Forward-confirmed reverse DNS failed tmxpmscs (in reply to MAIL FROM command)
這是一封「郵件無法送達」（Undelivered Mail Returned to Sender）的系統通知信。主要原因顯示為：550 5.7.25 Forward-confirmed reverse DNS failed。這通常表示您的郵件伺服器 IP 位址沒有設定對應的「反向 DNS」紀錄（Reverse DNS/PTR record）。
主要原因顯示為：550 5.7.25 Forward-confirmed reverse DNS failed。這通常表示您的郵件伺服器 IP 位址沒有設定對應的「反向 DNS」紀錄（Reverse DNS/PTR record）。