The SPF system functions as an additional layer in the mail transfer process. It establishes guidelines for approving and rejecting mail based on the message's origin. For instance, an ISP can publish a record listing the hosts and networks that are authorized to send messages on their behalf if they want to stop senders from their network from sending emails purporting to be from their customers.
Here's how to enable SPF for Zimbra if you use it to send emails to your clients.
For Zimbra, creating an SPF Record
With the Zimbra server, creating an SPF record is an easy process. You must add the IP address of your Zimbra server to your domain's SPF record, designating it as an authorized sending source, in order to prevent SPF authentication on the recipient's end from failing for emails sent using Zimbra.
Let's assume for the purposes of this post that a Zimbra server's IP address is ip4:x.x.x.x. Kindly swap it out for your Zimbra server's specific IP address.
Note: To enable SPF for outgoing emails using Zimbra, simply publish the aforementioned record if your domain previously lacked an SPF record. In case your DNS already contains an SPF record, you ought to update it to inculcate Zimbra as indicated below: