This article explains why some internet system may not be accessible from a LAN going through an SRX gateway, and how to remedy the situation.
 

Some of the web sites (like HDFC,government sites, etc), ftp servers hosted on the internet are not accessible from internal LAN via SRX gateway.

Setup
LAN  >>   [ LAN ip ] SRX [ Public ip ]  >> Internet resource (Web sites, ftp server, etc)
Source NAT enabled

Behavior
From LAN few web sites (like HDFC banking site, government web sites, etc), ftp servers are not accessible however able to access other web sites / ftp servers successfully.
LAN client side, packet captures confirms that (SYN) packets are sent out, but no (SYN+ACK) packet comes back.
 

Some internet facing Public IPs configured on an SRX may be listed in a Blocklist/Spam database and the web sites/ftp server being queried for access is enabled with Blocklist/Spam check. This results in the server dropping the connection request.

How to identify
Verify if the IP address is listed in Blocklist/Spam database (Google search keyword : “Blocklisted IP database”)


 

Get the Public IP removed from Blocklist/Spam database
Or
In SRX, use another Public IP address which is not listed in Blocklist/Spam database.