Recently, whenever I attempt to compose a message in Apple Mail, my entire system slows to a screeching halt and I have to shut mail down before I can have access to any other application. What's strange is that opening messages in my inbox and reading them has no effect on my computer's performance. I managed to boot up Activity Monitor during the most recent episode and it told me that Mail was using over 40 GB of memory. I'm no computer expert, but I'm fairly certain this is not supposed to happen. I've attached a screenshot for reference.

Activity Monitor Screenshot

Has anyone encountered a similar problem and been able to find a solution? Or does anyone have an idea what might be going on and have a recommendation on how to remedy the situation? If not, no worries, I can take my machine to the Apple Store, but hoping to avoid that journey if at all possible. Thanks in advance for your time and assistance!

Mail Activity Screenshot

  • I had a similar problem where Mail was continually accessing my works Exchange account. Start by going to the Mail app, and click on the Windows menu item and select activity. This will help show whats going on in the background. Report back. Jan 7, 2015 at 15:45
  • Do you have any Signatures defined which may have large images attached to them?
    – IconDaemon
    Jan 7, 2015 at 15:45
  • @FlyingTrashcan I've reproduced the issue and uploaded a screenshot from the Mail Activity window. Lots of synchronizing that wasn't completing. Jan 7, 2015 at 20:13
  • @IconDaemon my only Signature defined is a simple combination of text and hyperlinks. Do you think that could cause an issue? Thank you both so much for your comments. Looking forward to hearing more ideas if you have them! Jan 7, 2015 at 20:14
  • The Updating Cache message is out of this world! Almost 18.5 quintillion headers! That's 18.5 times the total number of grains of sand on Earth's beaches! Would you please tell us more information about the protocols you are using in your Mail client, how many accounts are involved, whether you use your own mail server, etc. With such hyper-inflated numbers, perhaps there is a Return Receipt loop or some other bouncing going on. It also seems to be doing a lot of toiling in the Drafts folder. What's in the Drafts folder?
    – IconDaemon
    Jan 7, 2015 at 23:11

1 Answer 1


try to change the download attachment setting to recent or none. Mail -> preference -> account -> download attachment -> 'none'/'recent'

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