The problem appears intermittent. We would like assistance in determining what is instructing your DNS servers to resolve netmail.pencor.com to 209.173.15.161.
That is coming from the authoritative name servers that the pencor.com domain uses.
It has three authoritative name servers listed, ns1.pencor.com, ns2.pencor.com, and ns3.pencor.com, and here, ns3.pencor.com seems to always be responding with 209.173.15.161:
$ dig +noall +answer A netmail.pencor.com @ns1.pencor.com.
netmail.pencor.com. 86400 IN A 209.50.150.224
$ dig +noall +answer A netmail.pencor.com @ns2.pencor.com.
netmail.pencor.com. 86400 IN A 209.50.150.224
$ dig +noall +answer A netmail.pencor.com @ns3.pencor.com.
netmail.pencor.com. 0 IN A 209.173.15.161
$
Giving different IP addresses can however be perfectly fine, such as for example an attempt from the team behind pencor.com to distribute (e.g. “load balance”) their traffic to different servers, to ensure proper capacity for all users.
However, in the specific situation as seen here, it looks more like their third name server (ns3.pencor.com) is out of sync, e.g. running an older version of their DNS data, and needs a forced re-sync.
If you’re looking to chase the discrepancy any further, you will need to contact the team behind the pencor.com domain, and ask them to make sure that all of their name servers are giving consistent responses.