Hi,
Is the problem with name resolution only ? or connectivity itself ? For example , are you able to ping the ip address 4.2.2.2 from SRX ?
If name resolution from the SRX is the issue ,
Is DNS Relay Enabled in CX111 (to pass DNS server information learned from ISP to SRX) ?
Enabling DNS Relay causes the CX111 to forward the DNS requests to the DNS servers of the ISP. If you disable this option, we need to set the DNS servers manually and these manually entered DNS servers override the server information provided by ISPs.
Please note that some ISPs may only allow the use of their DNS Servers only.