Invisible text in Mac Mail messages
I bought a new MacBook Pro with Catalina on it, migrated my content to it, and have been using Mac Mail on Catalina trouble-free for several months (and many years before that with other OS versions).
Suddenly a couple of weeks ago I started getting messages with blank areas of text and/or small bold question mark-in-a-box icons where actual content should be.
The text is actually there - I can copy it out and paste it into a text editor to read it. It's just invisible.
There is always some readable content in the emails - it doesn't affect all the content.
This seems to affect certain senders. Most emails look fine but so far 3 senders have sent me mail with invisible text.
Viewing raw source of the messages reveals no obvious tags or other reasons why this text should be invisible.
I tried disabling my Mail plugins (MsgFiler, Letter Opener, GPGMail) but that didn't change anything.
I also tried rebuilding the mailboxes containing the troublesome messages.
Restarting Mail or the Mac didn't help.
There was a recent Catalina update I believe - to 10.15.7. I wonder if there's a relationship.
Any thoughts?
MacBook Pro 15″, OS X 10.10