Hi Joao,
Regarding “an Exchange corporate account”, I’d like to confirm whether this is an Office 365 Exchange Online account or an Exchange on-premises server account. If it’s an Exchange Online account, please check Outlook Web App (OWA) to see if the same issue occurs.
Besides, I’ve tested it with my Outlook for Mac 15.6, and I didn’t encounter the issue you described. It did take a little longer to update the Sent Items folder than Outlook 2013 for Windows, but I didn’t have to restart it.
Since it works fine with Outlook 2013 for Windows and I didn’t reproduce the issue, we can determine this is an Outlook for Mac client problem (if you’ve tried OWA and it works fine too). In order to provide you with more dedicated support, please visit our Outlook for Mac client support forum. The engineers and community members there are the most proficient guys regarding Outlook for Mac client issues.
Thanks,
Allen
