Sounds like you have been sent a dodgy email that confuses Outlook. Please login to your mailbox via Webmail. Look for any suspicious email.
You should delete this email and any other emails with an obviously dodgy date/header. Don't forget to purge the Trash to remove any unwanted emails from your mailbox.
Now try again in Outlook
You should delete this email and any other emails with an obviously dodgy date/header. Don't forget to purge the Trash to remove any unwanted emails from your mailbox.
Now try again in Outlook