Error The Exchange certificate operation has failed with an exception on server . The error message is Access denied.

I am getting this error message when I am trying to open the certificate details from the Exchange 2013 ECP.
"Error The Exchange certificate operation has failed with an exception on server . The error message is Access denied. "
I am able to see the certificate details from the Power Shell.

How to fix the issue? 
After adding the Exchange Trusted subsystems as a local administrator on the server fixed the issue. 

Find out how many users are using Pop3 or IMAP in exchange Server (using log parser studio)

To Know the number of users connecting to exchange server for pop3 or IMAP , you have to enable protocol logging.

How to enable Protocol Logging?

Set-ImapSettings -Server "CAS01" -ProtocolLogEnabled $true
Set-PopSettings -Server "CAS01" -ProtocolLogEnabled $true

Restart the Pop3, Pop3 Back end, IMAP and IMAP Back end service.

Unless you change the path, you will find the logs in default path 

C:\Program Files\Microsoft\Exchange Server\V15\Logging\POP3

C:\Program Files\Microsoft\Exchange Server\V15\Logging\IMAP 

You can follow this document for enabling and limiting the log size.

Wait for some time, so the protocol log will be able to capture the logs. 

You can use log parser studio to analyze the logs. 

This small query can help you to find out how many users are connecting and accessing which mailbox. 

/*  New Query  */

select 
 user as Username,
 parameters AS Mailbox, 
 Count(*)
 FROM '[LOGFILEPATH]'
 WHERE Username NOT LIKE '%Health%' AND Username IS NOT NULL AND Mailbox NOT LIKE '%Health%' AND Mailbox IS NOT NULL
 Group BY Username, Mailbox
 Order BY Username