Our site mailboxes are configured and working but are not visible in user's Outlook clients or OWA. I have checked that the "Show in Outlook" is enabled. The users are mailbox owners and the mailbox is set to display when checked through EMS. 

[PS] C:\Windows\system32>Get-SiteMailbox | fl


RunspaceId              : aa8465fc-42b9-4896-b033-fb8c4281cc9f
Name                    : SM-MyNewTeamSite
DisplayName             : My New Team Site
PrimarySmtpAddress      : SM-MyNewTeamSite@domain.forest.com
Owners                  : {names of the 2 owners}
Members                 : {}
ShowInMyClient          : True
RemoveDuplicateMessages : False
MyRole                  : Owner
SharePointLinkedBy      : domain.forest.com/01_Users/User1
SharePointUrl           : https://domain.forest.com/MyTeam
Active                  : True
ClosedTime              :
RecipientTypeDetails    : TeamMailbox
EmailAddresses          : {SMTP:SM-MyNewTeamSite@domain.forest.com}
WebCollectionUrl        : https://portal.domain.forest.com/
WebId                   : 3a22cbf5-9570-4b90-8666-4c781e87b265
Identity                : domain.forest.com/Users/SM-MyNewTeamSite
IsValid                 : True
ExchangeVersion         : 1.1 (15.0.0.0)
DistinguishedName       : CN=SM-MyNewTeamSite,CN=Users,DC=domain,DC=forest,DC=lab
Guid                    : b492421c-a37f-4674-a0d0-31a71708b23e
ObjectCategory          : forest.com/Configuration/Schema/Person
ObjectClass             : {top, person, organizationalPerson, user}
WhenChanged             : 5/27/2015 4:50:04 PM
WhenCreated             : 5/27/2015 3:49:56 PM
WhenChangedUTC          : 5/27/2015 10:50:04 PM
WhenCreatedUTC          : 5/27/2015 9:49:56 PM
OrganizationId          :
Id                      : domain.forest.com/Users/SM-MyNewTeamSite
OriginatingServer       : server.domain.forest.com
ObjectState             : Changed

Removing and recreating the site mailbox doesn't solve the problem. Exchange 2013 SP1 CU8, 2 CAS/2 MBX in a DAG lab.