The funny thing is that steps to fix Outlook not opening the new "modern" Outlook worked fine, though, which made things even more confusing. We looked at the sign-in logs, tested new accounts, and eventually found what was really going on. Microsoft Outlook is one of the most widely used email clients globally, especially in professional and business environments. Outlook also comes with strong built-in security features, making it a reliable choice for managing communication and workflow.

One of the failed sign-in windows showed a long string under a field labeled Microsoft Information Protection API. Running that value through the Entra admin portal revealed what we needed. At that point, the focus shifted to what was happening during authentication. The answer came from a closer look at the Microsoft Entra sign-in logs and a hidden dependency that I wasn’t aware of.

If you would like a deeper explanation or step-by-step instructions, scroll down to the section covering your issue steps to fix Outlook not opening for more details. If you're committed to the task of Outlook troubleshooting in the meantime, let's get into our guide that will help you solve some of the most annoying Outlook issues. The classic Outlook consistently failed with CAA2000B or 4usqa, depending on the account state. However, when signing in using the new Outlook app, everything worked. Outlook sign-in failures started appearing in multiple tenants without any obvious cause.

The built-in back-off mechanisms in the indexing steps to fix Outlook not opening component of Windows Search or WDS pauses the indexing of Outlook data when the system is under heavy use. The easiest way to let the indexing finish is to leave Outlook running overnight.Additionally, you can reduce performance issues by running Outlook in Cached Exchange Mode. In this mode, Windows Search or WDS searches the local copy of the mailbox instead of the mailbox content on the server.

Configure your antivirus software to exclude Outlook files or processes from real-time scans to avoid interference. The AppData folder hosts a lot of files, including bookmarks and cached pages. This might be slowing down or overriding other commands in Outlook.

Both services offer robust features and are continually updated to enhance user experience and security. Outlook support for Mac refers to the resources and assistance Microsoft provides for users encountering problems with the Outlook application for macOS (Apple computers). Outlook webmail support is the assistance Microsoft provides for users who encounter problems using Outlook.com (formerly Hotmail) – the web-based version of Outlook accessed through a web browser. Outlook Inbox Support is designed to ensure users can manage their email communication effectively, leveraging Outlook’s features to enhance productivity and maintain organization within their inbox.

Outlook support for Windows is the technical support and resources provided by Microsoft for users of the Outlook application on steps to fix Outlook not opening Windows operating systems. Outlook, part of the Microsoft Office suite, is a personal information manager that includes email, calendar, contacts, and task management features. Support for Outlook on Windows encompasses a wide range of services designed to help users navigate and utilize the application effectively, troubleshoot problems, and enhance their productivity.

To determine whether this problem is caused by a corrupted user profile, create a user profile to see whether the problem still occurs when you use the new profile. When you start Windows normally, several applications and services start automatically and then run in the background. These applications and services can interfere with Outlook. A Selective Startup or "clean boot" process can help you identify problems that are caused steps to fix Outlook not opening by application conflicts.

Due to the large number of affected users, the automated fix took time steps to fix Outlook not opening to apply. Microsoft advised using a manual workaround to restore access more quickly. A notification will be sent once the incident is fully resolved. We can diagnose and fix several common Outlook connectivity issues for you. If our automated tool can't fix your issue, or you'd like to fix it yourself, see the next section. Sometimes, antivirus real-time scanning can slow Outlook down.

To sum up, we explored several methods to fix "Outlook won’t open" errors. Whether it’s a profile issue, a corrupted PST file, or faulty add-ins, the methods above can help you get Outlook running again. When Microsoft Outlook refuses to open, it’s incredibly frustrating. This issue often stems from common culprits like a corrupted user profile, a damaged data file (PST or OST), or even a minor conflict within its settings or add-ins.

These Outlook data (PST) files store user’s data, including email messages, calendars, tasks, journals, etc. By following these steps, you should be able to resolve the ‘Something is wrong with your data files’ error. Also, regain access to your email account and mailbox data. Once your task is done of locating the ScanPST.exe tool, kindly head to follow the below-given steps to fix Outlook data files (PST).