The Offline Address Book is updated by the Mailbox servers and serviced to the clients by the CAS servers.

CAS Servers distribute the OAB via the selected method every x minutes. These minutes are configured as the polling interval. This can be configured in the EMC via, Server Configuration > Client Access > CAS_SERVER > Offline Address Book Distribution > Right Click the OAB > Properties.

Mailbox Servers update the OAB and if there are any issues these they be logged in the Event Viewer on these mailbox servers. By default the logging level is set to ‘lowest’ and to view any useful information it needs to be at least ‘medium’. To change the logging level using the EMC go to, Server Configuration > Mailbox > MBX_SERVER > Manage Diagnostic Logging Properties (on the right) > Expand ‘MSExchangeSA’ > Click on ‘OAL Generator’ > Set to ‘Medium’ > Click ‘Configure’.

To update the OAB Manually in EMC go to, Organization Configuration > Mailbox > Offline Address Book tab > right click the OAB > Click on ‘Update’. Once this is done, and the logging level has been increased you should be able to see the logs on whichever Mailbox server is generating the OAB. If you look at the logs on the wrong server there will be an entry telling you which server is generating the OAB.

Once the logs have been enabled as above on the Mailbox server it should be relatively easy to find out what the issue is. In the Event Viewer (Application Logs, Source: ‘MSExchangeSA’, Critical/Warning/Error Events) of a mailbox server you should get an error telling you why a user was not added to the OAB.

ERROR: Proxy Address and Mail Attribute do not match.


OABGen will skip user entry ‘John Smith’ in address list ‘\Global Address List’ because the SMTP address ” is invalid.
– \Offline Address List

Often this will happen if the users primary email address is not the same as the ‘mail’ attribute in AD, the spelling has to be exactly the same.

Outlook will take a while to update it’s OAB or you can click on ‘Send and Receive’ > ‘Download Address Book…’. If this doesn’t work try deleting all the .oab files in ‘C:\Users\<username>\AppData\Local\Microsoft\Outlook\Offline Address Books’ on the machine where Outlook is running and then download the offline address book again.