Be sure to set the notification email from: address correctly in your site settings. The domain specified in the “from” address of the emails you send is the domain your email will be validated against.
Know how to view the raw source of the email in your mail client, so you can examine email headers for important clues. in Gmail, it is the “show original” option in the drop-down menu at the top right of each mail.
IMPORTANT: Does your ISP have a reverse DNS record entered to associate the domain names and IP addresses you send mail from? Test your Reverse PTR record here. If your ISP does not enter the proper reverse DNS pointer record, it’s very unlikely any of your email will be delivered.
Is your domain’s SPF record correct? Test your SPF record here. Note that TXT is the correct official record type for SPF.
Is your domain’s DKIM record correct? This will significantly improve email deliverability. Test your DKIM record here.
Returns the correct key
If you run your own mail server, check to make sure the IPs of your mail server are not on any email blacklists. Also verify that it is definitely sending a fully-qualified hostname that resolves in DNS in its HELO message. If not, this will cause your email to be rejected by many mail services.
N/A Using SparkPost
We highly recommend you send a test email to mail-tester.com to verify that all the above is working correctly.
Ok, a couple of errors, I’ll check out the DMARC record (first time I hear off it)
What I don’t get is that the test emails are coming through fine. Are those sent in a different way from the other emails?