In the event of the mail server being busy hung up on something(most of the cases, if you are sending/receiving a large email attachments), you may get a pop-up window saying “Server Timeout”.

The solution is to extend the amount of time Outlook will wait until it deems the sending/receiving to have failed. The default is 1 minute, so extending this to 5mins should do the trick

Here is an instruction how to change the Outlook server timeout setting:

In Outlook 2007 case:

1. From the Tools menu, select E-mail Accounts…
2. Select View or change existing e-mail accounts and click Next.
3. Select the e-mail you want to modify and click Change.
4. To bring up the Internet E-Mail Settings window, click More Settings…
5. Select the Advanced tab.
6. Left click on the slide-point and drag to the far right side (10 minutes). By changing the setting, you can avoid the above error message.
7. Click Apply and then OK.

In Outlook 2010 case:

1. Click on the orange ‘File’ tab.
2. Under the ‘info section, click on the ‘Account Settings’ button and then on the ‘Account Settings…’ option from the menu. The Account Settings window will open.
3. Under the ‘E-Mail’ tab, find the IMAP account affected, select it and click on the ‘Change…’ button (or double-click it)
4. Click on the ‘More Settings…’ button.
5. Under the ‘Advanced’ tab you will find the ‘Server Timeouts’ option.
6. Move the slider towards the right (long) to the desired value (5mins?)
7. Click OK and close all the windows.

Here are some screen shots: