This is typical when Sending RTF Reports with MS Access. Lines including cell lines in Tables, and border lines do not always show if at all. To overcome this problem, you and the recipient must use the Microsoft SnapShot Viewer. I believe it comes some with MS Office packages.
The other way to overcome this problem is to not use report formating that contains lines etc.
Self Taught In ALL Environments.....And It Shows!
... or consider using another reporting file format which does store all the details of the report as seen on your screen. Consider using a PDF writer. Occasionally however even the acrobat PDF writer can throw a wobbly and loose soem of the formatting.