Mac Mail doesn't work right on Sonoma

Since updating to Sonoma (one computer from Ventura, the other from Catalina), I have had two problems. 1) Most important. On both computers many emails arrive in Mac Mail (16.0) with the body empty. Web mail works, but I prefer to use Mail app as it helps me carefully file my email in folders. 2) On the computer updated from Catalina I am unable to flag emails at all. On the one updated from Ventura no such problem. Is there a mail remedy for these issues?