Weird Outlook behaviour when sending with right-click on file

Hello Team

when sending a file by right-clicking the file and then choosing the option 'Send To' and 'Mail recipient' Outlook takes approx. 30 seconds, then presents a pop-up that displays 'Retrieving mailbox settings' incl. a progress bar, as shown below

Then all my Reminders pop up, but I cannot do anything with them until I have sent the mail with the attached file. No button works ( for example clicking X in the top-right corner or 'Dismiss' or 'Dismiss All' . After sending the mail the Reminder window disappears. In the new Outlook I am never prompted for those overdue reminders, these are now called Events and I have no option or setting to dismiss these old 'Events' 

This is the new Outlook in a work / Exchange environment

Thanks

Peter