Mail confused by IMAP and loses messages

Thanks for your suggestion. Unfortunately rebuilding the mailbox only resulted in the "index" being updated on the Mac. When I click on the message, the same old deleted message appears instead of the new one. I still needed to go to my iPhone or iPad to see the message with your response.

Thanks for your suggestion. Unfortunately rebuilding the mailbox only resulted in the "index" being updated on the Mac. When I click on the message, the same old deleted message appears instead of the new one. I still needed to go to my iPhone or iPad to see the message with your response.

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Update... I just tried again rebuild the mailbox, and this time it worked. The new message content appears now when I click on the new message.

I will keep an eye on it to see if the problem reappears.

Unfortunately, the same problem has cropped up again less than half a day after rebuilding the mailbox. I deleted a message, then after some time had passed noticed a new message in iCloud inbox, so I clicked on that mailbox, and noticed the message I had deleted was listed in the index as a new message. I had to go to my iPad to check the mailbox to see what the real new message was. I hope apple can figure out how to fix this bug in their mail program.

Thanks for the suggestion here, but none of these articles shed light on the current problem, and I don't use webmail for my iCloud account. I already have multiple IMAP email accounts set up, and the problem occurs with other of my IMAP accounts as well, not just with my iCloud account. I have submitted a bug report to Apple.

I don't use webmail on any of the IMAP accounts that are exhibiting this problem. I do access these IMAP accounts from other devices (iPhone and iPad) which also use IMAP for these accounts. The applications on my iPhone and iPad do not seem to get confused like Mail on the Mac does. I have previously used the "Internet Accounts" control panel to delete and re-add accounts, but this did not resolve the problem. Also, I don't have any of those "cleaners" installed.

Let me further say that I even tried to use my iPhone to move one of these message to a different folder or even a different email account. The moved message appeared in the correct folder or mail account on both my iPhone and iPad, but on my Mac, the folder or mail account the message was moved to contained the previously deleted message that had appeared in place of the incoming message. Some cache file or directory is being reused by Mail on the Mac instead of downloading the new message from the IMAP server.

Thank you for your suggestion, and for the Feedback link. I have submitted feedback to Apple. I guess we wait and see if they eventually fix it.