Users who had been working normally suddenly steps to fix Outlook not opening received the CAA2000B error / AADSTS (after the token expired). Most Outlook problems can be resolved with proper troubleshooting and maintenance. Following the fixes above will help you keep your Outlook running smoothly and protect your productivity. We hope this guide proves useful in resolving your Outlook problems efficiently. Outlook accounts can have up to 100GB of storage per mailbox.
Out-of-date software and corrupted Outlook profiles are two of the most common issues that can prevent you from sending and receiving email. If you're an admin with multiple users reporting problems, you also should check for service issues with Microsoft 365. This kind of error usually indicates some issues on the disk where your Outlook PST file is located. It can be caused due to improper installation of a program, corruption in the hard drive or registry file, etc. This has nothing to do with the email client