Both I and my Mom have been having issues with blank emails since sometime last summer. I have a 27" iMac, she a MacBook Pro, both from 2017. She doesn’t live with me. We’re both on Monterey. The problems seem to have started on both computers at about the same time, so my guess is that is related to some MacOS update, though we didn’t think about it at the time, and at this point, I wouldn’t know which one it was.
I have email messages come in from 2 different mail servers, AT&T/Yahoo being one of them, but the problem occurs for all messages, not just Yahoo’s.
The emails open normally at first but after a couple of minutes, all text other than the FROM and SUBJECT goes blank: the body text in the side bar and the larger viewing window totally disappears. Clicking on a message to make it “active” also yields a blank window. After a couple of minutes, they all reappear and everything seems to work normally—until the next time Mail is quit and re-opened, though sometimes when other apps have been used and Mail has sat inactive for a while, there is a short lag before everything reappears.
Apple had given me a routine for occasional maintenance: Reset the PRAM and then re-open in “safe” mode to make sure all permissions are correct and whatever else it does. I’ve done that a few times in the intervening months, but the Mail problem continues (not that I did that to fix this problem, but just responding to drmoss_ca’s comment above).
I try to keep the INBOXES, SENT, DRAFTS, JUNK, and TRASH pretty uncrowded, so I wonder if it’s a memory problem of too many messages stored in permanent mailboxes “On My Mac.” One thought I had was: 1) to remove the various “On My Mac” mailboxes from ~Library/Mail; 2) delete the remaining files and folders; 3) re-enter all the account information for my various email addresses; and 4) slowly restore the other mailboxes to ~Library/Mail. I’m hesitant to try it out, though.
I also don’t think it’s related to log-in items, since my Mom doesn’t use any, and I only open with Calendar.
Unrelated Mail problem: In 2 of my email accounts (and not on all the AT&T accounts), Mail — on its own — renamed the Trash folders “Deleted Items,” so when you delete a message it doesn’t go into a Trash folder. So you can’t get rid of them by commanding “Empty Trash.” I deleted those 2 odd folders, figuring Mail would rebuild them, but that didn’t happen, so until I delete and re-enter the account information, I have to manually drag them to the “On My Mac” trash folder, which I forget to do occasionally.
Things on Macs sure have gotten more complicated than they used to be.