For future reference…
I was having an issue in which emails in a thread were not displaying the correct contents. This was happening primarily with my gmail IMAP account from the Standards Ebook mailing list which made it particularly frustrating.
I tried deleting and or rebuilding the mailboxes and even deleted the whole gmail mailbox (~/Library/Mail/v7/AFD4138D-113E-4798-BA9B-A928C0A9EC44/) all to no avail.
Finally I came across this Mail shows wrong message body (finding the right term to Google makes it so much easier…)
- Quit mail.
- Go to ~/Library/Mail/v7/MailData/
and any variants
- Restart Mail and let it rebuild (this will take some time).
So far this seems to be working…