How to prevent Gmail from rejecting your outbound messages

Back in November 2022, Gmail started requiring users sending out to Gmail accounts to set up their email with an SPF record. Why? Google email servers perform random checks on new sender messages to personal Gmail accounts to verify they’re authenticated. Any messages lacking either of these authentication methods will be either rejected or flagged as spam. Nevertheless, we strongly advise setting up an SPF record as a means to safeguard your organization's emails and comply with forthcoming authentication prerequisites.

For more information, you can check out Googles Support Article and view the links below:

What is an SPF record?
Does TierraNet have an SPF Record?