Recently I`ve started digging into mail server settings and the need for tighter security.
Some of the findings are startling ! I have found to my cost that not having the settings described below can cause major issues with sending and receiving email.
In recent years the large companies that deal with sending and receiving email have tightened the way that users can send email through their systems.
There is so much spam and phishing that the companies have tightened up the way that mail senders are recognised.
My findings below give some items that need to be looked at to ensure a free flow of email from and to your mail server.I use MXtoolbox.com to test out DNS and IP settings for websites and Mail server.
Should you find that you find the settings like this when checking your domains, it means you will often get issues sending and receiving email:
-- SMTP Open Relay May be an open relay.
-- DMARC Policy Not Enabled DMARC Quarantine/Reject policy not enabled
-- Status Ok SMTP Reverse DNS Mismatch OK - 220.127.116.11 resolves to mail--server.anycompnay.com
-- Status Ok SMTP Valid Hostname OK - Reverse DNS is a valid Hostname
Email Providers like Yahoo, AOL, BT, Google will block or delay messages that do not have DMARC Quarantinme enable, have an incorrect Reverse DNS name and most certainly can cause issues if it happens to be an Open Relay.
Check out how to verify below - all green is good.