How to solve "Outlook not responding" cases
"Outlook not responding" - Common reasons and solutions
Here are the most common reasons why Outlook may stop responding, popping up the annoying "end process" window or simply responding very slow to your input.
First of all, before looking for a complicated solution, try to optimize your Outlook mailbox using an optimization add-in such as Weight Diet for Outlook. Most of the times, Outlook stops responding due to a very large mailbox file that it's causing Outlook to require more resources than the computer can offer. Weight Diet for Outlook can restore your Outlook speed and stability by decreasing & compacting your mailbox file, making Outlook to require less resources.
Outlook.exe is suddenly resource-hungry
Scenario: Microsoft Outlook is probably the most complex email client software for Windows. Not only that it offers so many features, but it is also designed as a connectivity tool with other software or hardware products. As a result, it's stability also relays on 3rd party software (programs or drivers) - a badly designed piece of software can easily cause Outlook to require more and more system resources, until it crashes or it stops responding properly.
Solution: Restart Outlook. If the restart doesn't solve anything, try to close 3rd party programs that run at the same time with Outlook, maybe one of those programs is causing Outlook to require more resources. If the situation doesn't change, see below for more potential causes/solutions.
Third party Outlook add-ins
Scenario: Microsoft Outlook offers a complex mechanism for programming Outlook add-ins. Although the vast add-in majority is designed to help you improve your Outlook experience, sometimes 3rd party Outlook add-ins can cause Outlook crashes or they can simply conflict with each-other.
Solution: If Outlook generates errors or it is not responding after you recently installed an Outlook add-in, disable that add-in and see if it makes any difference (see how to disable an Outlook add-in). If Outlook starts to function correctly, look for add-in updates (maybe the installed add-in version was not designed for your Outlook version), contact the add-in developers for a solution or simply uninstall it for good.
Auto-archiving or syncronization in progress
Scenario: By default, Outlook is configured to automatically archive Inbox emails, so your mailbox file gets decreased. Also, when a communication device (such as a PDA or a mobile phone) is connected to your computer, on most cases Outlook will attempt to connect to it, via ActiveSync or 3rd party sync tools, in order to syncronize the Outlook messages and contacts with the mobile device. During the archiving or syncronization processes, Outlook needs more system resources and its response times are greater. If you keep performing actions on Outlook, causing it to require even more resources, sooner or later Outlook will not respond anymore.
Solution: While performing an autoarchive or syncronization job, it is advisable to allow Outlook to finish the task without inputing new actions. Usually, Outlook displays an additional icon on its status bar or on the Windows systray, while an autoarchive or sync job is in progress.
Using IMAP or Exchange accounts
Scenario: If you are using an IMAP or Microsoft Exchange email account, Outlook offers you some special abilities: download partial emails (email headers only) and the Outlook offline mode. If your Outlook session is not connected (online) on the Exchange server or if you configured Outlook to download/receive only email headers, you must be aware that it will take more time for Outlook to browse and display Inbox messages. That happens because Outlook needs to connect to your mail server and retrieve the rest of the message, so you can preview it.
Solution: Disable Outlook automatic email preview or configure it to always download full messages and to stay connected on the Exchange server. Even so, the IMAP send/receive process is slower than the regular POP3 send/receive process.
Oversized Outlook mailbox files
Scenario: The more emails you receive and store, the greater the Outlook mailbox file. As the mailbox file is increased, Outlook needs more and more time to open each mailbox folder. If you quickly browse folders while Outlook is still struggling to display their content, you will likely generate "Outlook not responding" messages.
Solution: Create some different Inbox subfolders and move Inbox emails to them. Use the autoarchive feature of Outlook to automatically backup older Inbox emails and put them away from your main mailbox file.
Outlook not responding when starting it
Scenario: When Outlook starts, it needs to locate and load your mailbox file and your Outlook profile add-ins (if any).
Solution: If you stored your mailbox file on a network location, make sure that network location is actually connected to your computer. Disable 3rd party Outlook add-ins and use the Outlook Detect & Repair function (or scanpst.exe) to automatically fix mailbox file errors.
Anti-spam and anti-virus programs
Scenario: "The road to hell is paved with good intentions". Obviously, all anti-spam and anti-virus programs are designed to keep you secure and away from junk or malware emails. However, an over-zealous anti-spam/virus program or too tight security settings can prevent Outlook or Outlook add-ins from functioning properly. For example, if you are using an email autoresponder program, Outlook must send automatic emails. This functionality can conflict with some anti-virus programs that incorrectly handle the automated messaging system as a virus that tries to send emails from your computer. As a result, the anti-virus will block the add-in and Outlook will stop responding.
Solution: Configure your anti-spam or anti-virus software to match your other Outlook add-ins, so they don't create security conflicts. Add Outlook.exe to the trusted executables list of your security / protection software.
Learn how to restore your Outlook initial settings.
Learn how to backup Outlook folders and Contacts.
To find out more about the Weight Diet add-in for Outlook, click here.
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