diff --git a/README.md b/README.md
index 6c77c3b..6e6d1ee 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,11 @@
 
 Runs postfix container.
 
-https://mxtoolbox.com/domain/
+- https://mxtoolbox.com/domain/
+- https://gmail.com/postmaster/
+- https://serverfault.com/questions/419407/fighting-spam-what-can-i-do-as-an-email-administrator-domain-owner-or-user
+- https://productforums.google.com/forum/#!msg/gmail/gcipz5Jg3zg/lrMCrt_kAQAJ
+- https://support.google.com/mail/answer/81126?hl=en&vid=0-1510561403600-1544997826763
 
 ## runit