Are you, by any chance, having Outlook force your incoming e-mail messages to plain text? Since a very great many e-mail messages are in HTML format when they get forced to plain text a lot of what was contained in them, particularly graphics, gets mangled. You also lose information that's involved with those graphics.
I always strongly discourage my clients from forcing plain text because of the potential for lost content that's hard to describe, but is there if you leave the message "unmolested" from its format of composition.
If you're not forcing plain text if an example of one of these messages can be forwarded to me I might be able to figure out what's going on just by examining what comes in.
Brian - Windows 10 Home, 64-Bit, Version 1803, Build 17134
Travel is fatal to prejudice, bigotry, and narrow-mindedness, and many of our people need it sorely on these accounts. Broad, wholesome, charitable views of men and things cannot be acquired by vegetating in one little corner of the earth all one's lifetime.
~ Mark Twain