The Sender Policy Framework (SPF) is used to prevent spammers from sending messages on behalf of your domain. With SPF, publishing authorized mail servers enables end-users to validate incoming emails via a simple DNS lookup. Combined with DMARC, you can leverage it to decrease the amount of spam you receive and improve your deliverability.
Adding an SPF Record for MessageLabs - Symantec (Broadcom)
Allow Symantec Email Security to send messages on your behalf by adding them to your SPF record.
Login to your DNS management console
Navigate to Tools & Settings > DNS Template
You need to edit the DNS TXT record related to SPF
An SPF TXT record for Symantec will have the following syntax:
yourdomain.com TXT v=spf1 include:spf.messagelabs.com -all
Publish this record in your DNS records section for your respective domain.
Note: If you don’t have an SPF record previously for your domain, simply publish the above-mentioned record to enable SPF for outgoing emails using Symantec. If you do have an existing SPF record in your DNS, you need to modify it to include Symantec, as shown below:
Previous SPF record: v=spf1 include:spf.zoho.com -all
Modified SPF record: v=spf1 include:spf.zoho.com include:spf.messagelabs.com -all
Wait for 24-48 hours to allow your DNS to process the changes