Symptoms

  1. New mails are not getting downloaded in outlook
  2. Outlook hangs at folder synchronization when the user clicks on Send/Receive
  3. The account is configured using IMAP 
  4. New mails are visible in the web client. 
  5. Mail sending is working from the web client


Possible Cause

  1. This issue can often be caused by a slow internet connection because IMAP is a bandwidth-hungry protocol and requires a steady and reliable connection.
  2. The issue is also compounded when the user has configured a lot of folders in Outlook. 


Resolution

The Outlook client has to be reconfigured with the following settings:

  1. The root folder path is set to Inbox
    https://docs.mithi.com/home/how-to-access-email-using-outlook-2013-application-on-your-desktop
  2. Subscribe only the required folders, unsubscribe all other folders
    https://support.booking-manager.com/hc/en-us/articles/360002089891-Outlook-Hangs-when-Synchronizing-Subscribed-Folders
  3. Change the keep offline messages configuration from Forever to 1 month
    https://docs.microsoft.com/en-us/outlook/troubleshoot/mailboxes/only-subset-items-synchronized
  4. Disable the auto syncing of the subfolders and only sync your inbox on send and receive.
    https://www.123marbella.co.uk/clients/knowledgebase.php?action=displayarticle&id=161
  5. This issue can still be noticed if you have a very large Inbox folder, Sent folder, Trash folder, or any subscribed folder. The recommended method of avoiding this outlook issue is to simply file away messages from these subscribed folders into archived / unsubscribed folders. You can simply archive messages in outlook to clean them out of your mailbox
    http://www.centennialarts.com/support/2012/03/13/how-to-archive-email-in-outlook/