反向DNS查询（PTR）
通过PTR记录查找与任意IP地址关联的主机名。
如何使用本工具
- 1
Type or paste an IP address into the input box, for example 8.8.8.8 or an IPv6 address like 2001:4860:4860::8888.
- 2
Click Lookup to send the address to our server, which runs a reverse DNS (PTR) query against the public DNS system.
- 3
Read the returned hostnames in the results list, or the 'No PTR record found' notice if the address has no PTR record or the lookup fails.
- 4
Try another address to compare results, for example a mail server IP versus a residential or cloud IP.
什么是反向DNS查询（PTR）？
正向DNS将主机名映射到IP（example.com → 1.2.3.4）。反向DNS则相反：它通过PTR记录询问“哪个主机名拥有这个IP？”。这对邮件投递至关重要：没有PTR记录的邮件服务器常常会被大型提供商（Gmail、Microsoft）当作疑似垃圾邮件来源而拒收。
常见使用场景
Confirm a sending mail server's IP has a valid PTR record before going live, since Gmail and Microsoft 365 often reject or junk mail from IPs with no reverse DNS.
Read web server or firewall access logs and turn raw IP addresses into hostnames to spot which networks or providers are connecting.
Verify that a cloud or VPS provider correctly applied the custom PTR record you requested for an outbound IP.
Investigate a suspicious IP during incident response to see whether it points back to a known ISP, hosting company, or CDN.
Sanity-check a newly delegated IP block by confirming PTR records resolve as expected after a network migration.
Troubleshoot SSH or service connections where the daemon does a reverse lookup on the client IP and a missing PTR causes slow or failed logins.