This may be somewhat helpful. I had someone forward me a group from her WINDOWS Outlook. From Outlook on my Mac I couldn't open the attachment or doing anything with it. When will mac stop sending security updates for imac 2011. However, I found that if I went online and logged into my exchange email account from the web, I could see the attachment and use it.

But still I couldn't see that group or save it in such a way that I could re-open it. However, I was able to open the attachment from Outlook on the web (on my Mac) and email the group from there.

Sooooo you may just have to save the original email with the attachment on your Exchange so you can get at that group whenever you need to. Not the best solution, but it's the least hassle, especially if the group is large.

For example, you can forward the group as a Vcard or Outlook contact, add notes about the group, email the entire group, or create a meeting with only those group members. In our case, we’re just going to click “Save & Close” to officially create the group and return to the main Outlook window.