Some email not coming through w/ Greylisting

Steve VH

Jan 29, 2017
cPanel Access Level
Root Administrator
I am a web designer and I provide hosting for a few dozen clients.

I am new to Greylisting in WHM.

I noticed yesterday an email is stuck in Greylisting for 17 hours. I checked in mail reports and see this:
[I]Deferred due to greylisting. Host: '' From: '[email protected]' To: '[email address]' SPF: 'unchecked'[/I]
I've read somewhere that some senders use multiple IPs, making a problem for Greylisting, and I wonder if this is such a case.

Or maybe that address US Govt / Medicare doesn't resend?

I know I can add that IP to Trusted Hosts, but I am wondering why it's not coming through.

I have an initial delay of 5 min and then 240 min Resend Acceptance Period and then a 30-day Record Expiration Time.

I'd appreciate anyone's helpful input! :)
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