Mavericks: Mail uses 100% cpu

I too have the same problem with Mail, and also with Safari (early 2011 MBP running Mavericks (OSX 10.9.1) . It did not start until I installed Mavericks. I've just abandoned Safari and use Chrome, but I have too much mail and account structure to easily abandon Mail. I have two different gmail accounts imapped.

The Mac becomes sluggish and the processor heats up, fan runs flat out. The activity monitor tells me the culprit (for Mail) is the Mail Web Content process. (For Safari, it was the Safari Web Content process.) This takes 100% CPU when things have gone wrong (<2% when things are OK). Also there can be up to 4 of these processes running concurrently, all trying to claim 100% of the CPU. Killing them cures the problem temporarily, but at least 1 comes back as soon as Mail app is touched. So I set out to try some of the cures above by first backing up with time machine. Then I emptied the (Mail) Trash and got rid of some unnecessary stuff in my inbox. The problem went away. A couple of days later it was back. I emptied the trash, it went away. A couple of days later ... yep u got it. So I looked at the trash. This sometimes contains hundreds of partial copies or echoes of sent mails. The longer the mail, the more copies you get, typically. Keeping the trash down and getting rid of what appear to be echoed files has kept the problem at bay for two weeks now. I'm not confident that this is the solution, but it's worked so far. Because both Web Content apps (Safari and Mail) seem to behave the same way, it seems likely that the bug lies with Mac OS or the apps, rather than gmail. A proper fix would be nice.

I have the same issue since i updated to Maverics.

I tried to eliminate multiple Sync Accounts for contacts (Google, Zimbra, ICloud), i tried to clean bad Fonts, i have reindexed all Mails, i have deletet all accounts an reintegrated them. - still the same Problem.

As i start writing Mails the CPU for the mail process gains up to 80-90% - this is ridiculous.

I don't want to change the mail client.

Is there any solution?????????

After a few days I have to conclude that my optimism was premature. Mail is OK sometimes for several hours, then develops the fault. The problem can persist for some time and then go away on its own. My conclusion is that some random event kicks the Mail Web Content process into a loop where it's searching for something it can't find. So Mail and Safari are both buggy. The "apparent" cures above were just fortuitous and Mail would have temporarily cured itself anyway.

The solution is for Apple to sort the problem out.

I hoped that the latest Marericks update (10.9.2) would cure the fault. For 2 days I thought it had, but sadly, no. The only partial solution Ive found is to run the Activity Monitor (from Utilities), click on %CPU to get the worst offenders at the top of the list and force quit all copies of the Mail Web Content process. You can still see the thumbnails in Mail, but the content from any open mail will disappear (from view, not from the universe). If you click on the thimbnail, Web Mail Content will restart (and may or may not demand 100% CPU) and you can read mail again.

This seems to have helped somewhat. The CPU use % in Activity Monitor is still high (70-90%), but at least Mail behaves more 'snappy'. Less spinning beach ball. But still the smart mailboxes take a 2 to 4 seconds to update. Annoying.

Darn, I really hoped that dtgiv's solution of just validating all one's fonts and getting rid of the bad ones would suffice, but 100% of my 653 fonts pass validation and no problems were found. Yet Mail continues to hog 100% of a CPU (and I've seen forays to over 200%).

MarkGD - FWIW, I've had Mail at 100% for days and days, then I did an Erase Deleted Items > In All Accounts... and that has actually dropped Mail down to < 4% for the first time in a good while. So I think there's something to your conjecture about getting rid of those deleted messages, partial and otherwise, being a viable temporary fix, even though as soon as you respond to a few more messages the problem is bound to recur.

This worked perfectly for the problem of Mail using 99.7% of cpu resources. It also seems to have slowed my fans, which is why I went looking for runaway apps in the monitor.

Thank you!

Actually, just 2 hours later and my mail is sucking up 100% of CPU and the fans are racing again, causing unexpected logouts.

I may have finally found something that works reliably. At least it's been a couple of days without Mail pegging CPU usage at 100%+. If you have multiple email accounts it's a bit tedious, because you have to make the changes separately for every account, but...

The whole of the solution: In Mail.app's Preferences..., click on Accounts, and then for each account on the left, turn off "Store junk messages on server" and turn off "Store deleted messages on server".

This means you won't be able to see mail you mark as Junk or that you delete on one machine on any other machine, but that's probably acceptable for most people. It certainly is for me. While I was at it I also set "Delete junk messages when:" to "One month old", so spam messages wouldn't stick around and clutter my Mac.

This also had the effect of removing a piece of "zombie spam"... A message in the Junk mailbox that kept coming back no matter how many times I deleted it. I know other people who've had this problem. I wonder if the problems are even related... Messages keep getting deleted and reinstated and a fresh search or some kind of reindexing takes place with each state change, or something like that.

In any event, my Mac has been running a lot cooler, for a couple of days now. I highly recommend giving this a try, if your CPU is still pegged or you're experiencing zombie spam.

The answer that worked for me is in Martin's Random Notes:

http://blog.martinshouse.com/2014/06/fix-for-100-cpu-use-in-apple-mail.html#comm ent-form

It worked completely!

cb

Thank you, thank you, thank you, thank you!! It appears that removing the "/" from the name of all labels in my gmail account has done the trick! It was getting REALLY bad and now that taken the "/" out of all label names, the CPU is no longer looping!! I had a persistent Spinning Wheel of Death (SWOD) that would interrupt me typing emails constantly. Mac Mail was hardly useable. Thank GOD for this fix! Thank you!

http://blog.martinshouse.com/2014/06/fix-for-100-cpu-use-in-apple-mail.html#comm ent-form

Just want to give an update. After a few months post the "font change" experiment and adding another gmail account to mac mail, I found my CPU was again heating up toward 100%... not good. Checked my fonts again, all 545 of them passed. However, after trying the fix from Martin's Random Notes (http://blog.martinshouse.com/2014/06/fix-for-100-cpu-use-in-apple-mail.html#comm ent-form) and removing the '/' on any of my gmail folders through gmail, it instantly fixed the 100% CPU issue.

Thanks Christopher Barker1 and RyanRayLA for recommending.

Good luck all!

I don't have Gmail account configured and I am still in trouble with full CPU usage, some news about this bug?

YES! This did it for me. Thanks. Now down to 0.5%