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Sorry, we have no information about host18-201-65-207.isdn.net. isdn.net is a domain controlled by three nameservers at isdn.net themselves. All of them are on different IP networks. Incoming mail for isdn.net is handled by four mailservers. All of them are on the same IP network. isdn.net has one IP number.

isdn.net
a records
 
+ 207.65.1.173 207.65.0.0/18 AS6203  
+ ---  
ns-soa records
ns4.isdn.net
+ 207.65.0.25 207.65.0.0/18 AS6203 -
+ --- -
ns records
ns4.isdn.net
+ 207.65.0.25 207.65.0.0/18 AS6203 -
+ --- -
ns5.isdn.net
+ 216.153.0.25 216.153.0.0/24 AS21922 -
ns7.isdn.net
+ 207.65.46.9 207.65.46.0/24 AS2828 -
mx records
isdn.net.s5a1.psmtp.com
+ 64.18.4.10 64.18.4.0/24 AS26910 s5a1.psmtp.com
+ --- s5a1.psmtp.com
isdn.net.s5a2.psmtp.com
+ 64.18.4.11 64.18.4.0/24 AS26910 s5a2.psmtp.com
+ --- s5a2.psmtp.com
isdn.net.s5b1.psmtp.com
+ 64.18.4.13 64.18.4.0/24 AS26910 s5b1.psmtp.com
+ --- s5b1.psmtp.com
isdn.net.s5b2.psmtp.com
+ 64.18.4.14 64.18.4.0/24 AS26910 s5b2.psmtp.com
+ --- s5b2.psmtp.com
ip numbers using ptr to this host
207.65.201.18