OPATH syntax for Exchange filter

[Lovedoktor]

Hi there

I would like to create a Dynamic distribution group called RedBlock.

In Active Directory when I select a user and view properties there is a tab labelled Attribute Editor.

In the Attribute Editor there is a Attribute called roomNumber which has the value RedBlock.

I would like the Dynamic distribution group to send mail to all users in RedBlock.

How do I do this using OPATH?

Likewise if I create a DDG called BlueBlock I want to use OPATH to access the AD attribute roomNumber and email any users with the attribute value BlueBlock.

I'm not too familiar with this at all so any syntax or guidance would be greatly appreciated.

Thanks

[#2]

The list of attributes you can use for filters is listed here: https://docs.microsoft.com/en-us/powershell/exchange/recipientfilter-properties?redirectedfrom=MSDN&...
As you can see, the RoomNumber attribute isn't one of them, so you cannot use it directly. You can however populate some other attribute, say extensionattribute5, with the value of roomNumber, and use it for the DDG filter instead.