Can't Send As from a distribution List.

[Daleos]

I'm having problems setting up a user that needs to send emails FROM an email address set up as a distribution list. 

I've gone into EAC > Groups >Distribution Lists
selected the distribution list, > Settings, > Edit Manage Delegates and attemptedto add the user there. but got a "Object reference not set to an instance of an object." error when tryingto add the user.

However, I could successfully added the user via the Classic EAC (Reciients > Groups > group delegation)

Even Powershell seems to think it's been added correctly

PS C:\WINDOWS\system32> Add-RecipientPermission -Identity email address removed for privacy reasons -Trustee email address removed for privacy reasons -AccessRights SendAs

Identity Trustee AccessControlType AccessRights Inherited
-------- ------- ----------------- ------------ ---------
OurCompany_OurCompany email address removed for privacy reasons Allow {SendAs} False

PS C:\WINDOWS\system32> get-RecipientPermission -Identity email address removed for privacy reasons

Identity Trustee AccessControlType AccessRights Inherited
-------- ------- ----------------- ------------ ---------

OurCompany_OurCompany email address removed for privacy reasons Allow {SendAs} False
OurCompany_OurCompany email address removed for privacy reasons Allow {SendAs} False
OurCompany_OurCompany email address removed for privacy reasons Allow {SendAs} False
OurCompany_OurCompany email address removed for privacy reasons Allow {SendAs} False

However I've still getting "You don't have permission to send messages from this mailbox." messages.

Is there any other settings Ined to enable to allow sending as distribution list emails?

 

[#2]

No, that's all you need to configure. Make sure to select the DG directly from the GAL when composing the message, do not use any stored From or autocomplete entry.