Comment 14 for bug 1721803

This morning I was able to receive the confirmation email on a @hotmail address. However, I am still unable to receive confirmation emails on other domains with differently configured mail servers.

I highly suspect that ending the spf record with '?all' does not suffice for some mail servers. As it is deemed as 'neutral' and not an actual 'pass'. The headers in the email I received at the @hotmail address back this up:

Authentication-Results: spf=neutral (sender IP is 23.253.72.95)
smtp.mailfrom=openstack.org; hotmail.com; dkim=none (message not signed)
header.d=none;hotmail.com; dmarc=none action=none header.from=openstack.org;

This tool can also be used to further validate spf records: https://mxtoolbox.com/SuperTool.aspx?action=spf%3aopenstack.org&run=toolpage

In my personal experience having a 'pass' on the spf record has a big positive influence on the amount of email that gets successfully delivered.