If you use SPAMExperts or another email filtering service that forwards to your cPanel mail server, you need to ensure that cPanel/exim doesn't check the SPF record for mail forwarded from your filtering server, otherwise legitimate mail will be bounced.

To do this:

• Login to WHM
• Go to 'Exim Configuration'
• Click on the 'Access Lists' tab
• Click on 'Edit' next to 'Trusted SMTP IP addresses'
• Add the IP of the filtering service
• If you are using SPAMExperts provided by VPSBlocks then add our SPAM Experts server IPs:
  • 203.143.85.209
  • 203.143.85.15
• Go to 'Restart Services' -> 'Mail Server (Exim)' to restart Exim to use the new configuration.