Google Suite or Google Apps. Not receiving email from few senders? How to troubleshoot the issue??

First Step:1. Check if the email was delivered to G Suite. To do this, log in as administrator to your Google Admin Console

2.  Go to ReportsAuditEmail log search.

 Now if the mail has been delivered to G Suite, mails will be listed in the log as shown below:

Again go to Admin Console and go the Groups

Now selected the mail receiver group to which the mail is not delivered

  In my case its group called 'Department Heads' . Go to Access Settings

Now go to Moderation Setting:

Then go to Pending messages under message. Mail waiting for moderation will be listed in the pending message: 

Here, we have to options:

1. Just post the pending message

2. Or Post the message and always future message from the author.