Steps to reproduce:

1. Install Agent on Windows
2. Try with correct DNS entries to get value from another machine:

   [root@c7zs1]# time zabbix_get -s 10.211.55.4 -k system.uname
   Windows VMZ 10.0.18363 Microsoft Windows 10 Pro x64
   
   real	0m0.052s
   user	0m0.003s
   sys	0m0.002s
   

3. Try with incorrect DNS entries to get value from another machine (the more incorrect entries you have, the more time you need):

   Server=qwerty123,qwerty123,10.211.55.39 
   

   [root@c7zs1]# time zabbix_get -s 10.211.55.4 -k system.uname
   Windows VMZ 10.0.18363 Microsoft Windows 10 Pro x64
   
   real	0m2.312s
   user	0m0.003s
   sys	0m0.002s
   [root@c7zs1]# time zabbix_get -s 10.211.55.4 -k system.uname
   Windows VMZ 10.0.18363 Microsoft Windows 10 Pro x64
   
   real	0m4.640s
   user	0m0.001s
   sys	0m0.003s
   

On Linux it's not a problem, since ncsd daemon will cache negative answers, but on Windows you can see errors like:

Get value from agent failed: ZBX_TCP_READ() timed out

By default, Windows stores positive responses in the DNS cache for 86,400 seconds (i.e., 1 day) and stores negative responses for 300 seconds (5 minutes).

Expected:
Do not fail with timeout with negative DNS in the Server= option.