Running Exchange 2010 and made changes to a Distribution Group - removed 3 users and added 3 different users (all people are Mail Contacts. When an Outlook user tries to email the Group - if the list is expanded, it shows old members and not new. list was edited this morning and on my station I could see the new users. others cannot yet. I ended up deleting the Group, recreating with new users and other users still see the original list.
Have restarted the Exchange File Distribution Service. If I log into OWA - the list is updated with the correct names. why did this work in OWA and not Outlook