Apple Mail "This Message Has No Content" Issue Resolution

I have seen so many people searching for a resolution to the Apple Mail "This Message has No Content" problem, so since I have finally fixed this issue for a client, I thought I would come here to post how I fixed this problem.

The issue, in my case, was related to corrupt files locally and/or in MacOS in Apple Mail.

Issue:

Mail would come into Apple Mail and it would show the sender, the subject, but below that it would simply say "This Message Has No Content". When clicking on the email to show it in the preview pane, the message area would be blank and would not show either the text of the images that were in the email. The emails that were affected seemed random. Some from the same sender and on the same account would have that error, while some would come through and render properly. It was all very random. I couldn't tie it to AOL. I couldn't tie it to Gmail, but I COULD tie it to Apple Mail. I was sure after deducing all other options.

Facts:

I was running a fully up to date MacOS Sonoma 14.4.1 on a 2020 Macbook Air. The issue existed before I upgraded to Sonoma from Ventura BTW.

I had 2 accounts in Apple Mail. One was a gmail account, the other was an AOL account. BOTH had random / occasional emails that would say this error.

Something that worked:

I had read people saying to drag the affected email out of Apple mail and on to the desktop of their Mac and open it from there. And sure enough this was a work around as the emails opened and rendered properly, but this was not a solid solution. But yes that's one way that it worked.

Resolution:

I created a test user account and added the email accounts to it and they worked properly. So now I knew that it was a corruption / issue directly related to his user account. So I went back to his main user account, went to internet accounts in System Settings, and removed both of his email accounts. I then closed Apple Mail.

Next I went to the user library directory by going to Finder and then choosing "Go" at the top in the menu bar. When in that menu, hold the "option" key to reveal the "Library" directory.

Next I went to Caches and deleted everything in there and then emptied my trash. After that I went into the Preferences folder and searched for all files with the word mail in them. I found 2 and I deleted those as well.

After all of that, I rebooted the Macbook Air, went into Apple Mail and re-added the accounts. As soon as I did I saw that everything was working properly and it fixed the issue for me.

I hope this helps someone. But be careful with these suggestions as I can't guarantee that they will work for you, and could actually cause damage to your files and / or OS. So follow these suggestions at your own risk. All I can say is that nothing on the internet solved my issue, but these steps finally did.

Good luck!