Maureen - Welcome to SillyDog.
If with an editor you were to look at an email that includes an attachment, you would find that the attachment is just a demarked segment of the entire email. So your statement that " ... it shows up ... " is the key. The 'showing up' is a 'viewing-time' option.
You didn't indicate what email client you are using, but in Thunderbird you can see if you have checked: View > Display Attachments Inline.
Additional note (it works this way for Windows / Thunderbird, anyway) - In either case you should also be able to see the icon that indicates the attachment. It will appear at the bottom of the pane that shows the email. If you don't see it, place the cursor at the bottom of the mail pane (this will be just above the Status panel, if it has been selected). The cursor will become double-arrow-ended; then move the cursor up slightly. The icon will appear. One then can click on the icon to manipulate the attachment as desired.
UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:18.104.22.168) Gecko/2008092417 Firefox/3.0.3