Receivers of my emails can see graphics

From Outlook I am used to copy-paste graphics into my messages. The receivers might have to confirm that the like to see/download graphics but they can certainly see the complete email including graphics (e.g. jpg) in the text. With EM Client this seems to be difficult. I get complaints from my clients and even when sending an email from EM Client too another account I have I do not get the graphics but just an empty rectangular.
What needs to be changed to make this working?

In menu/tools/settings/mail/compose, in the Mail Format section make sure both options are set to HTML and not Plain text.