Here is how to disable inline attachment previews and view as icon when composing new mail

OMG. Don't do this any longer. Microsoft/Exchange email platform has an issue with mixed style email content that this maneuver prevents Mac Mail from overcoming automatically (removes mixed styles) and so hides attached IMAGES of all kinds in received emails. Forwarding the emails reveals the images are there, but recipients don't know to do this and have no indication images are present in the email. It took me hours of testing to notice inline images was disabled when composing emails in Mac Mail. I had forgotten I did this years ago and now it is a nightmare. I changed "yes" to "no" in the terminal instruction below to turn it back off. Now my attachments are visible to Microsoft users, which is a lot of people now.

Previously posted in this support group:

There are many open topics for this issue so here is the short and working solution for Mail, at least in OSX Monterey.

1: you need to give terminal full disk access, System Preferences > Security & Privacy > Privacy > Full Disk Access, add Terminal and check it to be active.

2: restart terminal

3: enter the following terminal code which is mentioned several times before, but with full disk access for Terminal it is actually working now:

defaults write com.apple.mail DisableInlineAttachmentViewing -boolean yes

4: restart mail. Create a new email and now attachments are in icons not that annoying embeds.