How To Fix Email Service Unavailable Delivery Issues with IPv6 on Amazon Linux

Author: , July 16th, 2021

PROBLEM: Email delivery to Google was failing with a “Service Unavailable” error:

Note that the network address for the destination is shown as IPv6! That is the root cause of the issue: 1. Sendmail is sending mail from the IPv6 address instead of the IPv4 address 2. Google rejects IPv6 senders without proper reverse […]