It looks like you have a DNS Wildcard record for your domain.
*.econemon.com. IN A 18.104.22.168
This means that if a query results in no records, you'll get an A record for 22.214.171.124. Actually it is more complicated than that. If there is ANY record for a "label" (a fully qualified domain name, or FQDN) then that disables the wildcard record for that label. So, if you have an MX record for foo.econemon.com., a query for foo.econemon.com's A record will turn up nothing.
Wildcard records are somewhat rare and can confuse certain software systems. I don't recommend using them. However, your ISP is using them so that you don't have to bother them to update DNS records every time you add a subdomain. That makes sense.
Now on to your question...
What it seems like you are asking is, "If I have one nameserver with different data than the others, what will happen?"
Well, if you have 2 that your ISP runs with certain data, and 1 that you run with different data, then there is a 2:1 chance of getting data from your ISPs server. The DNS system doesn't keep looking to other nameservers if it doesn't find the data it wants in the first one. In other words, you can't ask Daddy if Mommy said "no".
This is an important concept in DNS. DNS needs to be FAST. Therefore, never do 2 queries when 1 will do.
That's why you should have the same exact zone data for a domain in each of the domain's nameservers. (Unless you have some funny load balancing scheme.)
- would a request for subdomain.econemon.com yield a
different address depending on which
name server you asked? (I guess it
- if so, this might actually be useful
to fall back to a "main server" if my
DNS was down, but how do I make the
client to use my name server when it's
The nameservers are tried in random order. If the first one doesn't respond, the DNS client will try the next one. When all have been tried the client gets a DNS error. Since each DNS server it sent 1 query, but generally we wait 30 seconds (I think) for a reply, if you have 100 nameservers, you'll be waiting 50 minutes before the client errors out. That's why I don't usually have more than 3 nameservers for a domain. More isn't better.
- would this mess up caching on the clients? (Probably.)
Not really. The software is very robust. Postel's robustness principle ("be conservative in what you send, liberal in what you accept") comes into play here. It has benefits. Do queries for www.yahoo.com, www.microsoft.com and www.google.com. You'll see that each nameserver gives different IP addresses depending on where you are in the world (and other factors). If that were to confuse clients, those sites wouldn't survive!