Loading photos from LDAP addressbook into Outlook 2013

We don't use MS Exchange and Outlook in general. Our mail server is IMAP and we have an LDAP addressbook.

We've put the pics in LDAP under the thumbnailPhoto property and if you use the Thunderbird mail client, the pics show up. However for certain users who use Outlook 2013, the photos don't load.

Is there something specific we need to do to Outlook to get it to load the pics from our LDAP addressbook (OpenLDAP)?

Every time I search, I can only get results for loading pics from Exchange.

Any help is appreciated.

Thx del.