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Most email clients these days offer the ability to utilize the IDLE function of IMAP. What the IMAP IDLE function does is leave a connection open on the mail server, then as soon as a new email has arrived it alerts the mail client and pushes the new message to the client.

In theory this sounds like a very good thing to have configured for your mailbox, unfortunately we've seen some problems with the way that Apple's Mac Mail handles this function of the IMAP protocol, it seems to leave open multiple IMAP connections instead of just one and over time they can pile up and become problematic.

So if you're using Mac Mail you might want to think about disabling this specific function, especially if you've received a notice from our system administration department regarding excessive resource usage coming from your IMAP activity.

  1. From the Mail drop-down, click on Preferences.

  2. Click on Accounts.
  3. Select your IMAP account from the list on the left.
  4. Click on the Advanced tab.
  5. Now disable the Use Idle setting.


That should be all that is necessary in order to go ahead and disable the IMAP IDLE function in your Mac Mail client. This should help ensure that your email client is causing any adverse problems on the server while it's trying to continually synchronize messages.


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n/a Points
2016-03-08 1:39 pm


Client is having issues with messages being marked as read after unsetting Mac Mail IMAP idle. Is there a workaround for this?





10,734 Points
2016-03-08 2:44 pm
That is certainly interesting, Dan. Are messages marked as instantly as read as they arrive? Or, are they briefly unread before changing to read? Is it possible the messages are being read by a differnent device on the same network?
n/a Points
2015-11-17 12:40 pm

Is the problem with Apple or is it with your software?

10,077 Points
2015-11-17 12:43 pm
Hello Lee,

This is a problem with Mac Mail specifically as it has affects on all email hosting providers.

Best Regards,
TJ Edens
n/a Points
2015-11-17 6:15 am

What is the state of this problem. Has Apple taken any action ?

Is it still a problem in El Capitan 10.11.1 ?



10,077 Points
2015-11-17 10:08 am
Hello Edouard,

Yes at this time, this is still a problem even with the new Mac Mail software.

Best Regards,
TJ Edens
2015-04-24 11:26 am
Has InMotion submitted this issue to Apple? I would imagine that you guys would be in the best position to do so since you handle lots of Mac Mail + IMAP issues - enough for you to write this!

thanks for the support so far.
n/a Points
2015-02-02 5:55 pm
Could this be a problem in iOS Mail as well? I don't see an IDLE setting in the iPAD and IPhone Mail settings. My Macs have IDLE unchecked, but I seem to be causing a problem with your servers.
n/a Points
2014-12-20 9:10 am
this option does NOT exist, at least in 10.10 Mac
n/a Points
2014-08-29 3:10 pm
In Mac Mail the Idle Command is grated out and cannot be unchecked. Because of this my Mac Mail will not get new mail unless you quit and restart or go offline then online.
31,313 Points
2014-11-10 12:06 pm
Hello Glenn,

Thank you for your question. This may be 2 separate issues, since Apple recently announced a known issue where "New email messages not received until Mail is quit and reopened." There is a work around included in that Apple article.

The "greyed out" Idle setting seems to be a problem with some email providers.

I tested on a Mac mail account connected to our servers, and this option is not grayed out. If your email is handled by us and this setting is not working, please provide more details such as your domain name, so we can investigate further.

If you have any further questions, feel free to post them below.

Thank you,

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