==== Required information ====
- iRedMail version: 0.8.4
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): LDAP
- Linux/BSD distribution name and version: Scientific Linux
- Related log if you're reporting an issue:
====
Where does iRedMail store DNS setup?
I changed the parameter "nameserver" in file /etc/resolv.conf from 192.168.0.1 to 8.8.8.8

[root@mx1 /]# cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 8.8.8.8
nameserver 8.8.4.4

But postfix request to 192.168.0.1 for the determination of MX records.
This occurs, when the check is performed reject_unknown_sender_domain in smtpd_recipient_restrictions

[root@mx1 /]# tcpdump -i eth0 dst port 53
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
10:48:51.390256 IP 192.168.0.122.59707 > 192.168.0.1.domain: 52552+ MX? yandex.ru. (27)
10:48:51.390596 IP 192.168.0.122.35064 > google-public-dns-a.google.com.domain: 59012+ PTR? 1.0.168.192.in-addr.arpa. (42)
10:48:51.408791 IP 192.168.0.122.46870 > google-public-dns-a.google.com.domain: 41542+ PTR? 122.0.168.192.in-addr.arpa. (44)

Why does postfix request to 192.168.0.1, if the parameter "nameserver" in the file /etc/resolv.conf is set to 8.8.8.8