Apple Mail can’t send images through Exchange properly

I have several accounts (iCloud, Exchange, IMAP) configured in macOS Mail. When sending messages containing images from my Exchange account through macOS Mail to other people in my organization (who are using Outlook) they can’t see the attachment. When sending the same email from Outlook for macOS they can see it.

This affects png, jpeg, etc. If I’m zipping the file it transfers properly.

This seems to be new since updating to macOS Sequoia 15.6.1.

I don’t have that problem with any other account.