Exchange user mailbox quota limit changes may take up to 2 hours to take effect

Open regedit on the server

Go to HKLM\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem

Create a new DWORD value “Reread Logon Quotas Interval” (without the quotes) and give it a decimal value of 1200 (20 minutes in seconds)

Still under the key ParametersSystem, create a new DWORD value “Mailbox Cache Age Limit” and give it a decimal value of 20

Restart the Exchange IS

Error when launching Exchange Management Console

Error reads: "...The system load quota of 1000 requests per 2 seconds has been exceeded. Send future requests at a slower rate or raise the quote for this user..."

Run command prompt as administrator.

Use IISRESET command.

After IIS restarts, try opening EMC again.