When you turn this setting on at your account level, it will show other Outlook users a notice that "A recipient has requested accessible content" when they send emails to you or carbon copy (cc) you on emails.
1. Log into your Outlook webmail (not desktop version)
2. Press the gear icon (Settings) in the top left corner.
3. Start typing in the search pane "Accessible Content," then choose that option when it pops up.
4. Check the "Ask senders to send content that's accessible" box.
