smtp helo/ehlo domain name DNS check failed

[MisterAG]

Can anyone point me in the general direction of what causes this error message? smtp helo/ehlo domain name DNS check failed. Starting last night, thousands of legitimate email was being blocked at the Fortigate. I have since disabled antispam protection on the Fortigate, and am now trusting our Barracuda to do the job on its own. Is this the Fortigate checking that the EHLO banner and dns hostname both resolve to the same IP address for the sending mail server?

[discoveryit]

disable Return e-mail DNS check and HELO DNS lookup in the Email Filtering in your protection profiles.

[MisterAG]

Tried that. In fact, I disabled every SMTP option in the appropriate protection profile, and it was still blocking! I ended up rebuilding the protection profile from scratch, and applying the new one. Things are curiously working now. I' m going through every setting to make sure that the two protection profiles are identical.