I was having issues with NetworkManager not properly setting the search option in resolv.conf even though I specified it in my EdgeRouter config. After some digging I found out that actually the issue is with dhclient not parsing the domain-search option. Apparently it prefers the domain-name option for that, which of course you can’t configure through the standard DHCP server config of EdgeOS. There are reports they are adding the option in a future version but for now you can use this method:

• In the config tree browse through ‘service / dhcp-server / shared-network-name / your-dhcp-name / subnet / w.x.y.z/ab
• Add a subnet-parameter option domain-name "your.domain.name";