Sending email on the internet can be impacted (often severely) by misconfigured or incomplete DNS records for your domain name. This can result in failure to deliver some or all of your outgoing email.
The following article describes best practice for setting your DNS records.
Best practice for DNS setup:
To avoid issues, you should ensure that the A record, MX record and reverse PTR record all match the hostname and domain (FQDN) configured in the server.
So for example – if we check these items for gordano.com
MX record lookup:
gordano.com MX preference = 10, mail exchanger = mail.gordano.com
A record IP address for mail.gordano.com:
mail.gordano.com internet address = 213.160.110.83
Reverse PTR lookup for IP address:
83.110.160.213.in-addr.arpa name = mail.gordano.com
Server hostname configured in Windows (correct):
mail.gordano.com
You should ensure also that you have a correctly configured SPF record to permit sending. You can use the tool SPF wizard for guidance, an example would be this:
"v=spf1 a mx ptr a:office.ntmail.co.uk mx:mail.gordano.com mx:gate05.gordano.com mx:vanguard.gordano.com ip4:213.160.110.83 ~all" spfwizard.net
If you are unable to make a change to your hostname on your server, you can review the article how to set outgoing hostname for GMS
If other changes on your system cannot be made according to this article, you should contact our support team who should be able to guide you through alternative more complicated methods to achieve a best practice result.