Why is there no access to the site from the local network?

Question

ubuntu

Previously, everything worked, but it seems like after installing iRedMail there is no access (the information is not 100%, I only noticed not long ago, although there was access before). What is available:
Ubuntu Server receives the Internet from pppoe, has the address 192.168.0.1, distributes it to the second network card. A WiFi router is connected to the server to the second network card and has the address 192.168.0.100. He conscientiously receives the Internet and distributes it to the local network. The router in the local network has an IP of 192.168.1.1, and the connected computers receive addresses 192.168.1.100-120. Everything works fine - the server gives the Internet to the router, the router distributes it to the local network. Apache2 is up on the server, 3 sites are spinning on it, access to which was previously both from the Internet and from the local network. After installing iReadMail, computers within the local network lost access to the Internet. Later it turned out that most likely, when installing iRedMail, the iptables rules were rewritten, after correcting them to those that were before installing iRedMail, computers began to receive the Internet again. And after a while it turned out that computers from the local network could not reach the sites on the server. How to fix? I don’t know what to attach to you, Apache logs are clean. Just in case:
sudo iptables -L -n -v

Chain INPUT (policy ACCEPT 2579 packets, 289K bytes)
pkts bytes target prot opt ​​in out source destination
66689 7350K fail2ban-postfix tcp -- * * 0.0.0.0/0 0.0.0.0/0 multiport dports
80,443,25,587,110,995,143,993,4675K 62 -dovecot TCP - * * 0.0.0.0/0 0.0.0.0/0 Multiport Dports 80,443,25,587,110,95,143,93,4190
62675 7146K FAIL2BAN-ROUNDCUBE TCP - * * 0.0.0.0/0 0.0.0/0 Multiport DPORTS 80,443,25,587,110,995,143,993 4190
1107K 1265M fail2ban-default tcp -- * * 0.0.0.0/0 0.0.0.0/0
1095K 1264M fail2ban-default tcp -- * * 0.0.0.0/0 0.0.0.0/0
Chain FORWARD (policy ACCEPT 75934 packets, 88M bytes)
pkts bytes target prot opt ​​in out source destination
Chain OUTPUT (policy ACCEPT 2796 packets, 453K bytes)
pkts bytes target prot opt ​​in out source destination
Chain fail2ban-default (2 references)
pkts bytes target prot opt ​​in out source destination
22 2280 REJECT all -- * * 115.239.228.15 0.0.0.0/0 reject-with icmp-port-unreachable
23 2200 REJECT all -- * * 115.239.228.13 0.0.0.0/0 reject-with icmp-port-unreachable
2190K 2529M RETURN all -- * * 0.0.0.0/0 0.0.0.0/0
0 0 RETURN all -- * * 0.0.0.0/0 0.0.0.0/0
Chain fail2ban-dovecot (1 references)
pkts bytes target prot opt ​​in out source destination
62675 7146K RETURN all -- * * 0.0.0.0/0 0.0. 0.0/0
Chain fail2ban-postfix (1 references)
pkts bytes target prot opt ​​in out source destination
62675 7146K RETURN all -- * * 0.0.0.0/0 0.0.0.0/0
Chain fail2ban-roundcube (1 references)
pkts bytes target prot opt in out source destination
62675 7146K RETURN all -- * * 0.0.0.0/0 0.0.0.0/0

hosts

127.0.0.1 mail.********g.ru ********-server localhost
127.0.0.1 localhost
127.0.1.1 ********-server
# The following lines are desirable for IPv6 capable hosts
::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
127.0.0.1 *********g.ru
127.0.0.1 **** ***s.ru
127.0.0.1 *******s.ru
127.0.0.1 ********g.ru

dnsmasq.conf

interface=eth1
listen-address=192.168.0.1
bind-interfaces
dhcp-range=192.168.0.100,192.168.0.100,255.255.255.0,24h
dhcp-option=3,192.168.0.1

disabled iptables - same thing.
this is what was noticed: if on the computer in the local network in the hosts file add

192.168.0.1 *********g.ru

or

ip of domain\server *********g.ru

, then this computer accesses this site from the LAN ... so it's in dnsmasq?
write what else to post to solve the problem

Answer 1

1) What DNS server is used by computers in LAN?
On Windows, it is checked with the ipconfig/all command
2) What do the following commands return on local computers:
nslookup sitename.ru
nslookup sitename.ru 192.168.0.1
?