When creating a newsletter please make sure that all of your references (in the HTML) to any images are absolute.  The images that you insert using the Insert Image icon within the editor can be made absolute in a few steps:

1. Click on the Insert Image Icon
2. If the image you wish to insert is not already uploaded to your web server (it does not appear in the list of files), click on Browse, select the image, then click on Upload.
3. Once the file is uploaded and appears in the list of files, select the file, set any additional parameters that you wish and click Insert
4. The image should appear in the spot where your cursor was
5. Click on the image to select it then click on the Insert Image icon again (you will notice that the "Image source" now shows the absolute path to your image) next click Update and you are done.

Any images that are used within the Template can be made absolute by editing the template from within iCMS, click on the HTML checkbox once to switch to HTML view, then clicking on the HTML checkbox again to switch back to WYSIWYG view and the editor should make the path to your images absolute.  The only images that you have to manually make absolute are any images that you set as background images.

In addition, when creating a Newsletter make sure that all text formatting (for the template and the newsletter) is done through the editor since your css file will not be available when the email is opened by the receipient.