You can authorize Microsoft Dynamics 365 to send emails on behalf of your domain by including them in your SPF record. To ensure the integrity of email sender identities, SPF uses a DNS-based mechanism that allows a domain to publish a list of IP ranges that should be treated as authorized.
Here is how you can setup SPF for Microsoft Dynamics 365:
Adding an SPF Record for Dynamics 365
Login to your DNS management console
Navigate to Tools & Settings > DNS Template
You need to edit the DNS TXT record related to SPF
The SPF TXT record will have the following syntax:
yourdomain.com TXT v=spf1 include:marketing.dynamics.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 Dynamics 365. If you do have an existing SPF record in your DNS, you need to modify it to include Microsoft Dynamics 365, as shown below:
Previous SPF record: v=spf1 mx -all
Modified SPF record: v=spf1 mx include:marketing.dynamics.com -all
Wait for 72 hours to allow your DNS to process the changes