In this link it's specified that "When you define a transport rule using a condition that expands membership of a distribution group, the resulting list of recipients is cached by the Transport service on the Mailbox server that applies the rule. This is known as the Expanded Groups Cache and is also used by the Journaling agent for evaluating group membership for journal rules. By default, the Expanded Groups Cache stores group membership for four hours".

Back in Exchange 2010, EdgeTransport.exe.config had to be modified in order to change the default "TTL" for the entries contained in the Expanded Groups Cache. An entry here describes the process, although the default time mentioned there (1h) is different than the one specified on this page (4h). This could maybe due to version differences targeted by the articles.

Does anyone know if there's a cmdlet which can be used in Exchange 2013 to modify how long entries are cached ? Or is it still up to modifying the same file as in Exchange 2010 ? I've looked at both Set-TransportConfig and Set-OrganizationConfig but didn't find any promising parameters.

Hi,

Based on my knowledge, I cant find any command in Exchange 2013 to modify distribution group cache settings. We can locate the EdgeTransport.exe.config file in the following directory: C:\Program Files\Microsoft\Exchange Server\v15\Bin. And change the settings to have a try:

https://technet.microsoft.com/en-us/library/ff360556(v=exchg.140).aspx

Please back up the EdgeTransport.exe.config file before doing any changes.

Regards,