Synchronizing folders

Outlook is constantly "synchronizing folders."

What is this?
How can I stop this? It's slowing down my computer!

Synchronizing Folders button“Synchronizing folders” is the generic term for when Outlook is sending and receiving messages and when (if your mail account type supports it) uploads changes to the mail server.

Under certain circumstances this process can “hang” and indeed cause your computer to slow down quite a bit. Below you'll find some common reasons for it and how to troubleshoot it.

Cause 1: Send/receive interval too short

Send/Receive All Folders buttonOutlook can automatically check for new messages on a set interval. When you set this interval too short, a new auto check will take place before the previous one can finish and thus the send/receive tasks can accumulate so that Outlook is basically stuck in an endless synchronization process.

You shouldn't set the automatic send/receive interval to less than 5 or even 10 minutes. When you have more than 3 POP3 and/or IMAP accounts I wouldn't recommend to set it shorter than 15 minutes. A good rule of thumb is to add about 5 minutes for every 2-3 extra mail accounts until you reach 30 minutes.

An alternative method would be to set 1-3 “high priority” accounts in a send/receive group which checks for new message every 10 minutes and all the other accounts in a separate send/receive group which checks for new messages every 30 minutes (or even longer)

You can set the send/receive interval in;

  • File-> Options-> section Advanced-> button Send/Receive…

Cause 2: Stuck message

Stuck in Outbox buttonWhen you have a message stuck in the Outbox, Outlook could end up trying to send that message until it succeeds. When it is truly stuck (for instance because it is too big), this of course will never work.

In most cases you can see the message and you can use these techniques to remove it. When you don't see the message, but Outlook still indicates it is trying to send a message at every send/receive interval, it could be a stuck Read Receipt and then you can use this method to remove it.

Cause 3: Virus scanner integration

Virus Scanner Integration buttonVirus scanners are a known source to cause all sorts of connection issues. It also applies in this case.

You should really disable its integration with Outlook as it doesn't offer an additional level of security anyway.

Cause 4: Check send/receive process

Show Progress buttonIn some cases it could be that just a single mail account is hanging. This could for instance be caused because the ISP for that mail account is down. In those cases you can contact your ISP and ask what is wrong.

You can sometimes also get an indication of what is going wrong when there is an error reported in the Send/Receive dialog box. When there is an error, the dialog box usually shows itself with the Error tab revealed. You can look at it manually as well via;

  • Send/Receive-> button: Show Progress-> tab: Errors
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