On 31/5/2017 10:51, Bert wrote:

In news
But even when I enter the server "name," I think my email and ftp
clients lookup the IP address on first access and store them for
future use, so it doesn't have to look it up each time

If they do, it's a bad idea.

Many large-scale systems (and some small ones) have multiple IP
addresses and rotate the way they appear to DNS requests in order to
balance user load.

They'll also take addresses out of rotation if systems are down.

I really don't know for sure. I never bother checking. But I do know,
the few times the Web didn't work and I knew DNS, or lack thereof, was
the problem, I could still get mail, etc.

I think the OP is having a configuration problem more than anything
else. I used to have a side business troubleshooting such things on
Windows machines. Windows has an extraordinary ability to break
itself. When the printer or ethernet or wireless, etc. just stop
working, particularly when they worked fine before the machine was
"turned off" the night before, settings were the first thing I
checked.

Stef