When testing Email Health using MX Toolbox, you might get 3 false positives:
 |
smtp | server.example.com | Reverse DNS does not match SMTP Banner |  More Info |
|
smtp | server.example.com | Warning – Does not support TLS. | More Info |
|
smtp | server.example.com | 15.077 seconds – Not good! on Transaction Time | More Info |
This is all hogwash. Actually MX Toolbox is being blocked by a security feature in WHM and therefor spits out the wrong information. The workaround is to allow the MX Toolbox server to query your WHM server by adding to Greylisting whitelist these IP addresses by “Trusted Hosts” one entry per line:
18.205.72.90
52.55.244.91
18.209.86.113
We’ll update this list as new IP addresses are reverse engineerd.
Rate Limiting Issue
If you run Email Health against the same server repeatedly, WHM might kick in with the following rate limiting message, and so in spite of you already have whitelisted the IP address, you’ll still see problems:
2023-02-13 15:04:58 H=keeper-us-east-1d.mxtoolbox.com [18.209.86.113]:29112 temporarily rejected connection in "connect" ACL: "Host is ratelimited due to multiple failure only connections (5.7/1h max:5)"