Sender Policy Framework (SPF) is a standard authentication method used to verify the sender of an email based on the details contained in their domains SPF record.
The following article can be used to assist in increasing deliverability of emails sent via Gateway by adding the following details to an SPF record, or whitelisting the URL/IP in your exchange settings. Though you will most likely not receive any issues when sending/receiving emails sent via Gateway, the following SPF changes can be made where needed.
Changes To Your SPF Record
For External Email Sent
1.You can add the URL spf.pstpf.com.au (149.72.130.154) to your DNS SPF Record.
E.g. v=spf1 include:spf.pstpf.com.au ~all OR v=spf1 ip4:149.72.130.154 ~all
For Internal Email Received
2. You can whitelist spf.pstpf.com.au (149.72.130.154) in Exchange/Exchange Online (O365).
Note: the following is only recommended for consideration by IT resources only. This should not be implemented by anyone unfamiliar with the intricacies of Exchange/DNS and the effect that these changes may have on your IT environment.