In the past week I have caught 4 external distribution lists that have somehow had their configurations changed from "Senders inside and outside of my organization" to "Only senders inside my organization".  At first I assumed it was only new distribution lists that were enabled within Exchange 2013 but I just noticed one that was originally enabled in Exchange 2007 long ago.  

Any thoughts as to what would be causing this to change?  I think the switchover occurred when I recently did a maintenance reboot of my two Exchange 2013 CAS servers, but i have no proof.

Are you sure nobody changed it by accident? Might be worth checked by the admin audit logs to avoid chasing your tail...

I checked that and there were no changes for as far back as the logs go, other than corrections to these settings.  In fact I see 3 more that were fixed already by someone else, so now I have 7 modified list.

Hi Jason,

Please run the following command to check the distribution group:

Get-DistributionGroup | FL Identity,RequireSenderAuthenticationEnabled

Generally, the RequireSenderAuthenticationEnabled parameter specifies whether to require email message delivery from authenticated senders. If the value is $true, messages are accepted only from authenticated senders. Valid values are $true or $false. The default value is $true.

If you want to change all distribution groups to "Senders inside and outside of my organization", please run:

Get-DistributionGroup | Set-DistributionGroup -RequireSenderAuthenticationEnabled $False

Regards,

Hi ,

To track the Admin related changes in exchange 2013 you can make use of admin audit logging and it will be enabled by default.

The audit log shows no one made any changes to any of these distribution lists before last week, and those changes that are logged are only the ones to fix the problem.

I just stumbled on another one that no longer works.  Unfortunately the list of those that are allowed vs not does not tell me which ones should be allowed and are simply "broken".  

Hi Jason,

Sorry for my delay. Has the issue been resolved?

Could you please share the command results here for further information:

Get-DistributionGroup | FL Identity,RequireSenderAuthenticationEnabled

Since there is no users changing this setting, please check whether there is any third-party program installed in your Exchange server. If that is the case, please disable it to have a try.

Regards,