Hi, Len Belanger Are you still getting this error message? Is it only occurring with PDF attachments? To open a private browser window, right-click on the browser icon on the taskbar and choose the option for a new private or incognito window. If yes, the problem is with your local cache - clear the browser cache. If no, You can use in-app support to bring it to the attention of Microsoft support. Based on the error message, it seems to be server side - * [https://support.microsoft.com/en-us/office/how-to-get-support-for-outlook-com-f5482a98-616c-4d44-b7c5-8aaaadf5c11a?ui=en-us&rs=en-us&ad=us] Please take a look, please hope it helps ; * [https://social.technet.microsoft.com/Forums/exchange/en-US/777b51ee-330d-43cc-a56e-4614d44aed7b/unable-to-access-owa-or-ecp-quotsomething-went-wrongquot-or-quot500-unexpected-errorquot?forum=exchangesvrclients] Thanks for reporting.