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Sorry, we have no information about a005.citus.nl. citus.nl is a domain controlled by two nameservers at citus.nl themselves. They are on different IP networks. Incoming mail for citus.nl is handled by one mailserver also at citus.nl. citus.nl has one IP number.

citus.nl
a records
 
+ 193.142.215.12 193.142.215.0/24 AS42755  
+ ---  
ns-soa records
dns1.citus.nl
+ 193.142.215.7 193.142.215.0/24 AS42755  
+ ---  
ns records
dns1.citus.nl
+ 193.142.215.7 193.142.215.0/24 AS42755  
+ ---  
dns2.citus.nl
+ 93.186.178.15 93.186.176.0/20 AS48539 -
+ --- -
mx records
barracuda01.citus.nl
+ 193.142.215.5 193.142.215.0/24 AS42755 -
+ --- -
ip numbers using ptr to this host
82.192.84.137