Connect to your domain registrar interface
MX records are set at your DNS provider which is usually the same as the domain registrar you’ve used to purchase your domain.
Delete previous “MX” entries
Delete all the previous “MX” entries you had registered for your DNS Zone, if any.
Add those MX entries
Add this TXT entry for SPF support
Value: v=spf1 include:spf.improvmx.com ~all