==== Required information ====
- iRedMail version (check /etc/iredmail-release): 0.9.3
- Linux/BSD distribution name and version: Ubuntu 14.04.3 LTS
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): nginx
- Manage mail accounts with iRedAdmin-Pro?: No
- Related log if you're reporting an issue:
====
Feb 15 20:49:41 mail postfix/postscreen[32057]: CONNECT from [2a00:1450:400c:c09::231]:34097 to [2a01:4f8:c17:25aa::2]:25
Feb 15 20:49:41 mail postfix/dnsblog[32062]: warning: dnsblog_query: lookup error for DNS query 1.3.2.0.0.0.0.0.0.0.0.0.0.0.0.0.9.0.c.0.c.0.0.4.0.5.4.1.0.0.a.2.list.dnswl.org: Host or domain name not found. Name service error for name=1.3.2.0.0.0.0.0.0.0.0.0.0.0.0.0.9.0.c.0.c.0.0.4.0.5.4.1.0.0.a.2.list.dnswl.org type=A: Host not found, try again

Google sometime chooses to use ipv6. In such cases there problems with checking white list at dnswl