It takes a number of seconds before Mac Mail marks a message as "read". I would like for it to take no more than 0.5 seconds, though instantaneous would be best.

How can I adjust the time required to view a message before it is no longer considered "unread"?

Mac OS X, 10.9.4 and 10.10

  • Please clarify if you are referring to Mail.app on Mac OS X (and if so, what version of OS X) or iOS (and again, which version of iOS). Your question references Mac but the tags reference iPhone. Thanks.
    – tubedogg
    Commented Oct 20, 2014 at 3:03
  • Great point thank you. iPhone actually does a nice job at instantly marking messages as "read". Commented Oct 20, 2014 at 3:08
  • I just tested this and the messages were marked as read instantly, using OS X 10.10. There are apparently no user preferences for this, and Apple removed a "defaults" preference at least two major versions ago, so I am not sure why you are seeing a delay. Is your mailbox very large/are there a large number of messages present? Are you using POP3 or IMAP with your email provider?
    – tubedogg
    Commented Oct 20, 2014 at 3:13
  • Brilliant! I am using IMAP. I disconnected from the network and it started marking them "read" instantaneously. I suppose when connected it waits for the server to mark it first. Thanks! Commented Oct 20, 2014 at 3:27
  • I added an answer that summarizes the result. If you could "accept" it as the answer, I'd appreciate it!
    – tubedogg
    Commented Oct 20, 2014 at 3:30

2 Answers 2


Have you tried quitting Mail, launching a Terminal and putting in

defaults write com.apple.Mail MarkAsReadDelay 0
  • The 0 in that answer is measured in seconds. In other words if you want Mail to wait a second before marking a message as read change 0 to 1 Commented Dec 28, 2014 at 16:12
  • Thank you!! Alas, at long last, this is the real answer. What is the default value of this setting, and must the value be an integer? Commented Mar 5, 2015 at 13:04
  • 7
    Unfortunately this no longer works in Yosemite. Apple removed this setting. Commented Jul 12, 2015 at 9:50
  • 1
    Is there an equivalent in El Capitan/Sierra?
    – P Varga
    Commented Aug 9, 2016 at 12:08
  • 1
    Mac OS 10.12.6. this works defaults write com.apple.Mail MarkAsReadDelay 0 Instantaneous message as "read" on a IMAP account while online. works perfectly
    – Roped
    Commented Jul 24, 2017 at 9:56

When utilizing an IMAP account, you may see a delay in marking read when connected to the mail server, as it issues the mark read command to the server first and waits for a response before doing so locally.

  • Good point - even with the local mail client marking it as read, there can be network delays to foil that quick action and revert the status to unread.
    – bmike
    Commented Jul 24, 2017 at 10:20

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