There is a problem with your mailboxes!

I am having the same exact problem and I'm searching on here for a solution. When I click "rebuild" nothing happens and when I try to open mail again, the same thing happens.

What are some good trouble shooting steps for this?

Quit Mail.

In the Finder, select Go To Folder (Shift>Command>G). Paste below into window:

~/Library/Mail/V2/MailData

Select the Envelope Index Files and move them to the desktop.

Open Mail and hit continue to rebuild the messages index.

You need to be sure you're in your Home Library folder. Following the above should put you there.

The Home Library is hidden in Lion:

Try this: In the Finder, select Go from the menu and hold down the option key. Select Library from the submenu.

In this Finder window, navigate to Mail folder/ V2 folder/ MailData folder.

Before going further, quit all applications and open Disk Utility. Repair permissions and Verify Disk. If Disk Verification comes back OK, reset your Home Folder permissions.

To reset your Home Folder permissions, follow this:

1. Turn on the Mac whilst holding down cmd + R. You can let go once you see a spinning dial. You will then see the ”Mac OS X Utilities” screen.
2. On the top menu, click Utilities, then click Terminal.
3. Type resetpassword and press Enter.
4. Click on your main hard drive.
5. In the dropdown box under “Select the user account” make sure to select your username.
6. Underneath where it says “Reset Home Directory Permissions and ACLs”, click the Reset button.
7. Press cmd + Q to quit the Reset Password application.
8. Press cmd + Q again to quit the Terminal.
9. Press cmd + Q one more time and click Restart.

Try Mail and also recheck for those files.

upgraded to mountain lion from lion, everything was going ok until one time i launched mail and got this error every time, removing all "envelop index" files from Mail folder/ V2 folder/ MailData folder. Did it for me, thanks.

After three long days of troubleshooting, lots of questionable advice, and much gnashing of teeth, I stumbled onto this advice. Did both of these things (resetpassword and replacing the Envelope Index files) and boom, it worked. Mail re-imported my messages and I was up and running. Glenn Leblanc, whoever you are, may the sun of a thousand mornings shine on your life. THANK YOU.

Glad that helped you.

I appreciate the gesture of "the sun of a thousand mornings shining on my life", but instead I'm sitting here listening to the sound of hurricane Isaac pounding on my house walls. On the bright side, maybe those mornings will happen.

Thanks

Glenn Leblanc - THANK YOU!

I had to spend 3 hours of my precious spare time fixing this problem with my mail, and it was only after I had done the resetpassword and replaced the Envelope Index files (which you posted) that the problem was solved.

Someone else wrote somewhere that they missed Steve when they were complaining about the same problem. I must say that I tend to agree. One of the greatest things about Apple products has always been that they just work immediately with no annoying problems at - or after - installations and upgrades. I have been a happy happy Apple user for 10 years now, and it is only recently that I have had several frustrating problems like this one. But thank goodness that there are people like you out there who can help. Thanks again!

Glad that helped you. Don't get too frustrated because of a problem. It happens no matter who you are.

If you really want to feel frustrated, buy a PC with Windows 8. Every time I have to install something or fix a PC, it really makes me appreciate my Mac.

You are absolutely right! I should go and buy myself a PC and then start that up when I am frustrated with Apple products :-) My point was only that Apple products seem to have taken a turn for the worse recently, but they have definitely still not sunk to the level of a common PC :-)

That said - I have another frustrating problem which you might be able to help me with? I know this is probably not the correct place to post it, but I would very much like to hear if you have a solution:

I attempted to open up my iphoto yesterday and discovered that the recent update has managed to make (almost) all of my photos disappear. I panicked for a few minutes because I have not done a backup since my Time Capsule broke down about 9 months ago, but then I found them in another user profile on my imac, so I know that the photos are still there - just not showing up when I open iphoto in my default profile. I received some sort of message along the lines of: "you cannot view photos with this version of iphoto" and then I had to "upgade" or "quit". I chose the first option and... presto!... I only had 20 photos in iphoto - instead of 8000.

Do you have any idea what I can do to bring all of my photos back? Someone suggested that I should download the 9.1 version from the Apple website, but I haven't tried that yet. Sorry for troubling you with another issue - unrelated to the originial post - but judging by my recent experience, you are the best apple-problem-solver available on the internet :-)

First thing you should do is to make a backup to an external drive of at least all users so you won't lose any data.

Not understanding finding them in another user. You are saying you have more than one user profile? If so, are you storing the same photos in more than one user, or possibly storing them to the other user library?

Under edit in the menu, choose swtich to library and verify you are viewing the correct library in the path.

If your library is correct and photos are not there, but are in the other user account:

You can log into the other user, copy the iphoto library and files to the desktop of your main user or to an external drive, then log back into the default user and move or copy it to the Pictures folder replacing the present one.