Incoming Email from certain senders is taking much longer than other emails?

[SidedTech]

I am on the newest CENTOS 7.4 kvm, and cPanel v66.0.25 and noticed that my outgoing email is immediate, like within a second to the place I send it.
When I respond, via Gmail or a few other free email providers like Yahoo! and very rarely another email on a different self hosted server, it will take about 30 seconds.

However Best Buy (for example) needs to send me a confirmation code, or PayPal, etc, the email takes almost 20 minutes, sometimes even longer.

I know the question has been asked, but I can't seem to find an answer specific to this situation.

Thanks in advance.

 

[Infopro]

GreyListing is probably enabled on your server. The docs should be of some use to you:
Configure Greylisting - Version 68 Documentation - cPanel Documentation

 

[SidedTech]

I disabled greylisting, and the emails are still taking 20 minutes from Best Buy, etc. I even tried re enabling and changing the rules of the greylisting, etc. Nothing has changed. Thanks though for the response.

 

[cPanelMichael]

Hello,

You may want to generate a test email from one of those remote servers, and then monitor /var/log/exim_mainlog for the message to see how it takes for Exim to accept it (and to see if there's anything related to the delay). EX:

tail -f /var/log/exim_mainlog

Thank you.