Image appears blurry

Hi,

I’m not sure what I’m doing wrong, but when I select the image to appear in a smaller size, like “thumbnail” or “medium”, the image still appears the same size as when I select “mailchimp”. The only difference is that they appear very blurry.

This is in the email campaign preview mode in Mailchimp, I still haven’t send any actual campaign because I’m afraid the image will appear blurry in the actual email.

When I choose “mailchimp” the quality of the image is good. But I would like to have a smaller image.

I hope that you can help me with this issue.
Thanks!