Hi Barbara:
To copy and send an email, try dragging your mouse over everything you want to copy (hilite). Select the Apple (command) key and the C key simultaneously. This will add the highlighted text to your clipboard. Open a new mail form and position your cursor in the text box. Select the Apple (command) key and the V key simultaneously. This should paste the initially highlighted text into the mail form.
As an alternative, after highlighting the text to be copied, in your mail program go to Edit on the toolbar, select copy in the pull down menu, open a new mail message, go back to Edit in the toolbar and select paste in the pull down menu.
Either way should do the trick.
You didn't say what type of attachment won't open.