The case of missing distribution group members in users Outlook GAL / OAB

I recently ran into a very peculiar issue. I had users on outlook 2007 & complaining about missing entries for distribution groups. Now keep in mind that until now we have been using Exchange 2003 w/ Outlook 2003, 2007, and 2010 and no issues at all.

So we start migration of some 2003 mailboxes to 2010. Keep in mind 2010 SP1 has been configured for weeks with no 2003 mailboxes showing signs of this issue...

So I go to test this in OWA with a test 2010 mailbox. Well I don't see anything wrong every user that should be there according to get-distributiongroupmember -identity "DL-AllHandsNYC" is there? What are the users smoking? OK I pull up Outlook 2010 and yep they are right missing entries. Now normally I would send a test email and see if the missing members get the mail and stop there, but I must make them viewable.

So maybe an issue with 2010 sp1 OAB distribution? Nope!

There are massive numbers of objects with the "hiddenfromaddresslistsenabled" attribute set to $true!!! How has this not been an issue until now?

The behavior was only noticed when our 2010 mailboxes started beta testing the system.

Long story short the fix is easy:

The solution: set "hiddenfromaddresslistenabled" to $false

get-recipient -recipienttype MailContact -resultsize unlimited -filter {HiddenFromAddressListsEnabled -eq $true} | set-contact -HiddenFromAddressListsEnabled $false

get-recipient -recipienttype UserMailbox -resultsize unlimited -filter {HiddenFromAddressListsEnabled -eq $true} | set-mailbox -HiddenFromAddressListsEnabled $false

get-recipient -recipienttype DistributionGroup -resultsize unlimited -filter {HiddenFromAddressListsEnabled -eq $true} | set-distributiongroup -HiddenFromAddressListsEnabled $false

get-recipient -recipienttype PublicFolder -resultsize unlimited -filter {HiddenFromAddressListsEnabled -eq $true} | set-publicfolder -HiddenFromAddressListsEnabled $false

Some objects were corrupt and get-recipient -resultsize unlimited -filter {HiddenFromAddressListsEnabled -eq $true} will show you any left over items that need repair/conversion.