How to instruct Splunk Ent. to ignore sending alerts about missing Forwarders?

[SamHTexas]

During my health checks I usually get a list of missing forwarders, I have found that these forwarders were on a few de-commissioned servers that are no longer around. But Splunk repeats the missing FWs. How do I tell it to ignore certain FWs reporting

[s2_splunk]

You should be able to remove these zombies by rebuilding the forwarder assets lookup: 

Monitoring Console -> Settings -> Forwarder Monitoring Setup -> Rebuild forwarder assets

If you want to disable the alerts completely, read up here.