My ATT IMAP Mail account will not receive mail unless I rebuild the mailbox.

Run Connection Doctor (window menu) when it starts press the Show Detail button, then press Check Again.

See what it says.

Also post the settings you are using for the account (obscure your email address and name)

Have you removed the account and created it anew?

Sorry, can't be much help, these forums are littered with non-functional ATT and Yahoo accounts (and you have both in one)

Maybe another will have a suggestion for you.

Quit Mail. Force quit if necessary.

Back up all data. That means you know you can restore the Mail database, no matter what happens.

Triple-click the line below on this page to select it:

~/Library/Mail/V2/MailData/Envelope Index

Copy the selected text to the Clipboard (command-C). In the Finder, select

Go ▹ Go to Folder

from the menu bar. Paste into the box that opens (command-V), then press return.

A Finder window will open with a file selected. Move the selected file to the Desktop, leaving the window open. Other files in the folder may have names that begin with "Envelope Index". Move those files, if any, to the Trash.

Log out and log back in. Relaunch Mail. It should prompt you to re-import your messages. You may get a warning that the index is damaged and that Mail has to quit. Click OK.

Test. If Mail now works as expected, you can delete the file you moved to the Desktop. Otherwise, post your results.

AT&T uses Yahoo for mail service, and Yahoo often causes problems with Mail in OS X, so there may not be a good solution. You can try the following.

Please follow these directions to delete the Mail "sandbox" folder.

Back up all data.

Triple-click the line below on this page to select it:

~/Library/Containers/com.apple.mail

Right-click or control-click the highlighted line and select

Services ▹ Reveal

from the contextual menu.* A Finder window should open with a folder named "com.apple.mail" selected. If it does, move the selected folder — not just its contents — to the Desktop. Leave the Finder window open for now.

Log out and log back in. Launch Mail and test. If the problem is resolved, you may have to recreate some of your Mail settings. You can then delete the folder you moved and close the Finder window. If you still have the problem, quit Mail again and put the folder back where it was, overwriting the one that may have been created in its place. Post your results.

Caution: If you change any of the contents of the sandbox, but leave the folder itself in place, Mail may crash or not launch at all. Deleting the whole sandbox will cause it to be rebuilt automatically.

*If you don't see the contextual menu item, copy the selected text to the Clipboard (command-C). In the Finder, select

Go ▹ Go to Folder...

from the menu bar, paste into the box that opens (command-V). You won't see what you pasted because a line break is included. Press return.

wjackman wrote:

I'm convinced that the problem is with Mail itself (rather than ATT) because Mail on my iPhone and iPad work fine - all messages come promptly. That suggests to me that the problem is Apple Mail.

You're correct. I have the same issue with my ISP (Cox IMAP). Cox started offering IMAP mail a couple of months ago and like you, my iPhone receives and sends mail immediately like my previous POP setup. But on OS X using the Mail app, it won't receive immediately but will send immediately. So, what I've done is add the Tool Bar button to "Take All Accounts Offline". I click it to take my mail account offline then click it again to bring it back online. Or I use Mail/Synchronize all mail accounts. Both of these allow me to keep the Mail app open and periodically check email. Or I Quit Mail and reopen it.

I tried the Thunderbird mail client and it does not have the issue that Apple Mail has. I can send/receive immediately from Thunderbird all the time. So, I agree with you the issue is an Apple Mail issue. By the way, the issue is not just the Mail app in Mountain Lion. The issue also exists in Snow Leopard and Lion's Mail app.

There are so many reports of strange problems with Yahoo and Mail that I've pretty much given up on the whole subject. If you take email seriously, I suggest you use a better service provider -- which is to say, anything but Yahoo or AOL. If you want to continue with Yahoo, use webmail or try another mail client. One has already been mentioned. I don't use it and have no opinion about it.

You won't believe this, but it helped me...

After months of issues with ATT/Yahoo mail I called support again regarding issues of delayed sending of messages.

I was told that ATT/Yahoo mail doesn't work well with IMAP at all. They had me convert my Yahoo email account to POP. I don't know if it is an improvement or not.

Currently, I have problems, as well.

When I open Mail, I look at the Activity window (Window/Activity) and see Opening Mail box, Evaluating message 47 of 255. It goes through all the messages and then starts again in an endless loop.

You might want to consider starting a new discussion. Since this one is marked solved, less people are likely to look at it. You can link to this one.