Microsoft Outlook is one of the most advanced, yet complex email client software. It provides great flexibility by acting as a connectivity tool for many professional software. However, such software or a professional Outlook add-ins are not reliable and can lead to improper functioning of the Outlook. The Outlook is designed to archive Inbox emails to reduce the mailbox size. However, the mailbox size increases as more and more items are added. Due to this, Outlook struggles to provide a smoother access to user mailboxes and can eventually end up “Not responding”. In addition, the advanced security settings in anti-virus programs can also prevent Outlook in functioning properly.

There are many other reasons for “Outlook Not Responding” error. Such errors are quite frequent if the Outlook hangs or freezes while sending or accessing a mail.

Some of the common causes of “Outlook Not Responding” error are mentioned below. 

• The Outlook is outdated
• The Outlook is being used by multiple processes.
• Conflict in the add-in installed with Outlook.
• Heavy mailbox.
• Any sort of corruption in Office programs.
• Corrupt or damaged Outlook data files.
• Conflict in the antivirus software with Outlook.
• Corrupt user profile.
• Conflict with any other program with Outlook.

All the above-mentioned causes and the corresponding error message occurred in earlier versions along with the recent Outlook 2013 and 2010. So, in order to overcome the common issue of “Outlook Not Responding” error from all the versions, you need to have a common solution that works for Outlook 2013, 2010, 2007 and earlier versions.

Mentioned below are some of the common solutions that can be tried.

1. End Outlook.exe process

If the Outlook is being used by multiple processes, you can kill the hanging process. This can be done by following the below mentioned steps.

1. Start the Windows Task Manager by either by pressing Ctrl + Alt + Del, or by right clicking the taskbar.
2. Choose “Start Task Manager“.
3. Switch to the Processes tab.
4. Choose the OUTLOOK.EXE by clicking on it.
5. Hit the “End Process” button.

2. Start Outlook in Safe mode

Starting Outlook in safe mode is yet another solution that is worth trying. Safe mode loads the Outlook without any add-ins and customization files. This can be done by following the below mentioned steps.

1. Hold down the Ctrl key and click on its icon or open the command line and type outlook.exe /safe.
2. Click Yes to confirm that you really want to start Outlook in Safe mode.
3. If the above steps resolve your issue, the problem was most likely with one of your add-ins.

3. Disable your Outlook add-ins

If you experience the “Outlook Not Responding” error for the first time, then try turning off the recently installed add-ins one-by-one. In order to turn off the add-ins in Outlook 2007, follow the below mentioned steps:

1. Go to the Tools menu
2. Click “Trust Center“ and choose ’Add-ins’
3. Click Go

In Outlook 2010 and Outlook 2013, follow the below mentioned steps.

1. Switch to the File tab
2. Click ‘Options’
3. Choose ’Add-ins’
4. Click Go

Finally, uncheck the add-ins and close the dialog.

4. Close all open programs and applications

Since Outlook is a complex application, it requires a lot of resources. In addition, it does not have the required memory to perform a required operation, which can eventually lead to “Outlook Not Responding” error. A simple solution is to close all other programs that are not required at that moment.

5. Repair Outlook data files

You can always use the inbuilt utility to overcome many issues faced in Outlook. The Outlook comes with an efficient Inbox repair tool, which scans your damaged or corrupt Outlook data files and automatically repairs it. In order to use the Inbox Repair tool you need to follow the below mentioned steps.

1. Close Outlook.
2. Navigate to the C:\Program Files\Microsoft Office\OFFICE14 folder if you are using Outlook 2010 and C:\Program Files\Microsoft Office\OFFICE15 for Outlook 2013.
3. Double-click Scanpst.exe.
4. Click “Browse” to select the Outlook data file.
5. Choose the scan options by opening the “Options” dialog box.
6. Click “Start” when you are done.
7. You can initiate the repair process, in case it spots any errors.

But sometimes, Inbox Repair Tool does not work and you can not repair your outlook PST file. In such scenario, you can use Stellar Phoenix Outlook PST Repair software. You can get this software from following official webpage:

http://www.stellaroutlooktools.com/scan/pst-repair.php

6. Reduce the size of your mailbox

With the accumulation of mail and its associated items, the Outlook mailbox grows in size. This can also make the Outlook irresponsive.

There are few simple ways to handle this problem.

1. Create multiple folders as Outlook takes more time in displaying items from a single folder while you are navigating to another folder. In this way, you can organise your mails as well as avoid any concerning errors.
2. Compact the Outlook data file by following the below mentioned steps.

1. If you are using Outlook 2010, go to the Compact option on the File tab, under Info > Accounts Settings >Data Files tab.

2. Choose your Personal folder.

3. Click Settings.

1. Click Compact Now by going to the General Tab.

If you are using Outlook 2013 and 2010, you need to follow the below mentioned steps.

1. Right-click the Personal folder.

2. Select Data File Properties > Advanced>Compact Now.

3. Another way of reducing the file size is archiving your old items.

7. Synchronize Outlook without interrupting

While Outlook archives or synchronizes messages and contacts with your other devices, do not take any actions in Outlook during this period. This will allow Outlook to perform the archiving or synchronization process smoothly without giving any error.

8. Disable antivirus software

Outdated anti-virus or anti-spam programs are one of the main reasons for Outlook issues. These programs often conflict with Outlook and prevent them from functioning properly. It is always recommended to update the anti-virus from time-to-time. In addition, make sure that the Outlook add-ins are added to the trusted applications list of your protection software

9. Repair your Office programs

In case none of the above solution works, try repairing your Office programs. Follow the below mentioned steps to repair the Office programs.

1. Close Office applications.
2. Open Control Panel.
3. Right-click on the Microsoft Office under “Add or Remove Programs”.
4. Select Change.
5. Choose Repair
6. Click the Continue button.

Credit : http://www.stellaroutlooktools.com/blog/how-to-fix-outlook-not-responding-error/