Welcome to the forum.
First, Save_As, and choose a format like PNG, or JPEG. Then, just Attach that image in your e-mail client, like Outlook, or other.
Now, depending on your POP service, there might be a file size limit on your end, or the recipient's end, and if you run into that, then instead to Image>Image Size, and Scale the file down. You can also do Save_For_Web to strip out unnecessary data, and compress quite a bit. Try again.
As Bill says, it depends on your email client. If using Outlook, then simply drag your image file onto the email. I believe Outlook Express has a feature thatautomatically downsizes image files. I drives my wife crazy when she gets images emailed to her for the family history books she creates, and they are only 600 pixels on the long side. My own ISP gets the grumbles when emailing large images files, and tends to crash with several full res JPGs attached. Zipping then up usually helps, but I have found it safer to use a file sharing site, or I now ftp the files to my own - never ever updated - Wordpress site, and send a link.
So it's horses for courses. What are you riding?
If you wanted to email directly out of Ps CS5, you could try this panel from Russell Brown's Script's page. Check out the video (http://av.adobe.com/russellbrown/AdobeEmailer_SM.mov) and see if this is what you were looking for. I can't recall if this panel's installer had problems with Ps CS5.1.