Outlook OWA exchange not syncing when I delete

I use Outlook Mac 2011 v 14.2.3 and OWA with a hosted exchange to push my email info to 4 devices (iMac, laptop, iPad, iPhone). All worked perfectly until a couple of months ago, when I had a big freeze due to being too close to my storage capacity. I got it functioning but I have 1 residual issue. When I delete an email message on my iMac by clicking the delete button, it does not sync. The email remains on OWA & my 3 other devices.  Clicking delete works fine on my laptop, i phone & ipad; and the sync works if I drag the email to the trash on my imac. But clicking the Delete button on my iMac only deletes the email on my imac (not the owa server, not my other devices). I've done all the suggested things (deleting preferences, rebuilding the identity, etc) except for a total un-install and re-install of office. Any ideas? Thanks!