請問 最近收到一封日本客戶提供被退信的內容如下
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電子郵件系統無法傳送郵件，但是未回報明確的原因。請檢查地址後再試一次。若仍然失敗，請連絡您的系統管理員。
<xxx.domain.com #5.0.0 smtp;554 Service unavailable; Client host [123.231.123.101] blocked using dul.dnsbl.sorbs.net; Dynamic IP Addresses See: http://www.sorbs.net/lookup.shtml?123.231.123.101>
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看起來是因為被sorbs 擋信, 但我在SORBS FAQ 上看到需先確認DNS反解是否正常
我透過 ping -a ip 出現要求等候逾時 但用 nslookup ip 及 domain 測試正反解 都ok , 以及以下這段訊息 , 請問要如何修改及確認以下訊息的TTL 呢?
另外我已經發信請sorbs 解除封鎖 但沒有下文 ,
請問各位會先做那些步驟確認自己沒問題後再提出申請?或是有其它更好的解決方式呢?

附註: 因為客戶僅提供訊息,公司user 希望我們能幫忙解決這個問題
故實際問題,是發生在對方那邊
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Additions/Submissions to the DUHL Exclusion List

We also operate a self-help exclusion interface that allows the owner of a system to quickly exclude a single IP address (or, in some cases, multiple IP addresses) from the DUHL. For this to be possible, the following criteria need to be met: •The MX record of a domain needs to contain a host name that maps to the IP address involved. The Time to Live of the MX record needs to be at least 43200 seconds.
•The A record for the host name needs to have a TTL of at least 43200 seconds.
•The reverse DNS PTR record for the IP address involved needs to map back to the name given in the MX record, and to have a TTL of at least 43200 seconds.
•If there are multiple MX entries, these rules apply to them all.
When all these conditions are met, please go to https://www.au.sorbs.net/scgi-bin/dulexclusions to request quick exclusion for your mail server.
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