How to give write access to a user to a DL using PowerShell

I would like to give write access to a user to a DL. I am using below command.

Add-ADPermission -Identity "Group Name" -user "userName" -AccessRights ExtendedRight -ExtendedRights "write"

but I am getting error Extended write "Write" was not found.

send as write works fine using below command , but how to give write access.

Add-ADPermission -Identity "Group Name" -user "userName" -AccessRights ExtendedRight -ExtendedRights "send as"

NOTE: Its Exchange 2010.