The default SMTP port (25) may be blocked by some Internet Service Providers (ISPs) due to spam concerns. Currently, you can't use Outlook on Windows to edit calendars that are shared with your Outlook.com step-by-step Outlook troubleshooting account, even if you've reconnected your Outlook.com account to Outlook. We're working to make it possible to edit shared calendars in Outlook 2016 for Windows. If you are having issues sending email, this might be due to validation issues with your Microsoft Account.

Bug fixes, new features, and performance enhancements are released regularly. Sometimes, a weak or unstable internet connection can cause Outlook to misbehave. To check if this is the issue, temporarily disconnect from your Wi-Fi or unplug your LAN cable, and then try opening Outlook again. If you receive a connectivity error, your network might be to blame.

If you're having problems setting up your email in classic Outlook, we want to help. Find solutions to common problems or get help from a support agent. If you can't open Outlook, or Outlook disappears or crashes, one of your add-ins may be to blame or you may need to update Outlook. You can give feedback by selecting Help from the top menu, then Feedback. If your mailbox is full, we won't be able to reply to your request.

If the network is performing slowly, Outlook must wait for read and write operations to the AppData directory to finish. We recommend that you move several items in your larger folders to separate folders, or that you archive those items by using the AutoArchive feature. Make sure that the latest updates for Outlook are installed. For more information, see How step-by-step Outlook troubleshooting to install the latest applicable updates for Microsoft Outlook (US English only). For more information, see Support for Office 2016 and 2019 clients connecting to Microsoft 365 services has ended. Running the /resetnavpane command removes all customizations to the navigation pane.

We are aware that some users may not be able to receive email from Gmail accounts. Although it's not possible at the moment to turn the feature off entirely, you can choose to remove it from your favorites list by right clicking the folder and selecting Remove from step-by-step Outlook troubleshooting Favorites. This issue has been fixed for Outlook.com country domains.

All these things can come together and make Outlook slow. It’s not just one thing causing the problem – it’s a mix of reasons that make Outlook not work as fast as it should. If step-by-step Outlook troubleshooting you can't open Outlook, or Outlook disappears or crashes, one of your add-ins may be to blame or you may need to update Outlook. Visit Firefox support to learn how to Disable or remove Add-ons.

Outlook.com (the web version of Outlook) and Outlook apps require a 1st party alias (Outlook/Hotmail/Live/MSN) to send and receive email, use calendar, etc. Occasionally, classic Outlook tries to run a process in the background. Auto-archive, sending and receiving a very large attachment, or running some of the other mailbox tools step-by-step Outlook troubleshooting can all be done in the background. Check the status bar at the bottom of the screen to see if another process is running. If so, wait a short time (usually two or three minutes) to see if Outlook starts working again.

To access the calendar shared with your Microsoft 365 for business account, you'll need to accept the invitation from Outlook on the web, iOS, or step-by-step Outlook troubleshooting Android. If you've already clicked the Accept button in Outlook 2016, you won't be able to re-accept the invitation from another Outlook application. The person who sent you the invitation will need to remove your permissions and then send a new invitation. This issue has been mitigated and we are continuing to monitor the issue to ensure stability. The root cause was the deployment of an incorrect campaign data file, which led to false positive campaign detection. We have since reverted to the right data file and the outbound email flow has returned to a normal state.

If the self-help doesn't solve your problem, scroll down to Still need help? Switch your alias to an Outlook.com or Hotmail.com account. Customers using the contact support buttons at the foot of the support pages, or the "email us" links in support Virtual Agent, are unable to open the Help Pane. Check that you have not accidentally blocked the Gmail domain when blocking one Gmail user. Connect with experts, discuss the latest Outlook news and best practices, and read our blog.

Large cache is often the cause of corruption, reduce the risks by reducing the size of the cache. For more information about performing a clean boot, see How to perform a clean boot in Windows. For a list of antivirus software vendors, see Consumer antivirus software providers for Windows. Outlook stores certain data, such as email signatures and the spelling checker dictionary, in the AppData folder. If the network is performing slowly, step-by-step Outlook troubleshooting Outlook must wait for read and write operations to the AppData directory to finish.