I'm using Apple Mail 16.0 (36220.127.116.11.1) on a MacBook Air (13-inch, 2017) with macOS Monterey 12.6.2 (21G320).
I don't know when it started but there's a problem I have since some months:
Sometimes when I click on an e-mail in the list of e-mails, no matter in which folder (inbox, sent …), the header (from, to, subject, date) gets shown as usual but the e-mail content is empty, just white space.
This happens with all my e-mail accounts. All of them are IMAP accounts. All these e-mails are already downloaded and often only a few KB in size. It's the same with e-mails with and without attachments. There's no "This message has no content" message or similar. This also happens when I disable the internet connection. When that happens the content preview in the e-mails list is visible as usual as well as the e-mail header. Only the mail content is blank.
Sometimes I just have to wait a few seconds to see the content. Sometimes I can make the content visible by clicking on another e-mail and then back to that e-mail. But often I have to restart Apple Mail.
This not only happens to one e-mail but often to multiple e-mails simultaneously. I click from e-mail to e-mail and they all show that behavior.
Rebuild didn't help. Also reinstalling macOS (keep data but reinstall macOS) didn't help. I even completely erased the system, made a fresh install of macOS, and then restored data from a backup. (I'm pretty sure my problem would be solved if I'd make a fresh install and then import data and make the settings manually instead of restoring from a backup but I cannot do that currently.)
Do you have any idea how to solve that problem? Is there any error log I can check?