Cannot Start Microsoft Outlook

Users with delegation access to multiple mailboxes are randomly but frequently getting the following error when opening Outlook 2013:

Cannot start Microsoft Outlook. Cannot open the Outlook window. the set of folders cannot be opened. Microsoft Exchange is not available. Either there are network problems or the Exchange server is down for maintenance.

Microsoft had us create a new throttling policy with an RCA Max Concurrency of 500 to raise the limit of allowed connections and assign it to the end-user.

This allows the end-user to close and re-open Outlook when necessary, but the error will reoccur if Outlook is closed and reopened repeatedly, which would max out the number of allowed connections again. Each delegate mailbox takes up as many connections as the main mailbox.

[PS] C:\>New-ThrottlingPolicy -Name ThrottleTest -RcaMaxConcurrency 500 -ThrottlingPolicyScope Regular

Name                                    ThrottlingPolicyScope                   IsServiceAccount
----                                         ---------------------                             ----------------
ThrottleTest                          Regular                                           False

[PS] C:\>Set-ThrottlingPolicyAssociation -Identity mailboxUserName -ThrottlingPolicy Throttletest