I know I will forget this is I don’t post it somewhere.
When creating a new DL using the Exchange 2010 management shell I like to set the Notes attribute with some background as to why the DL is being created or how it should be used. The Notes attribute (actually AD attribute “info”) shows up in the General tab for the properties of the DL in Outlook so users can see something useful about the DL.
1) You have to set a value for the Notes attribute on the New-DistributionGroup cmdlet when creating a new DL using the -Notes paramater
2) You have to use the Set-Group cmdlet to change or update the Notes field if the DL already exists.
What tricked me for a bit was that other objects e.g. Contacts use the Set-Contact command to add/update Notes for both new and existing Contacts, but for DLs the Set-DistributionGroup cmdlet does not support a -Notes parameter, you have to use the Set-Group cmdlet which I hadn’t really come across before.
I found the good answer here: