All our software products work by querying whois servers that listen in on port 43. However, Domain Name Analyzer and Domain Name Analyzer Pro have options to minimize the number of whois lookups by first checking if a domain name resolves to an IP address. This information is used to decide if a whois lookup is required. There are cases were the ISP will always resolve domain names to an IP address. The software will automatically detect this and prevent errors.
Our products do support lookups through proxy. However, these will have to be a script setup by you on your servers.
You can use these software products to quickly lookup a large number of domains for availability.
You should be aware that most whois servers restrict the number of connections and lookups from a single computer. This means that you should be very careful while looking up a large number of domains at high speeds. Some registrars provide special options to lookup large number of domains for availability. You can configure our software to make use of such services.
There is no limit on the number of domains you may lookup.
The simultaneous connection limit allows you to configure the number of whois connections the software will make at any instant. If you make a list of 500 or 1000 domains, the software will check all of them but will make sure that no more than the set number of connections are active at any time. This prevents flooding the whois server.
The number of simultaneous connections and the connection interval (interval the software will pause between the lookups) is very important. If you are not careful you could end up being banned by whois servers. So it is always better to set the number of connections low and connection interval high.
Yes, you can. Use the "Config Tab > Whois Config" ("Preferences" menu option in Mac versions) for this.
Please see Whois Setup for more details.