How might I easliy reduce the file size of screenshots included in my emails using Outlook and Exchange

I frequently have the need to quickly paste screenshots in emails sent to our office Exchange server to a large number of recipients. Using ALT-PrtScn works like a charm but the file size when I send the email is usually about 4MB a picture. I imagine it is because the clipboard uses a raw image. Is there a way to automatically or very easily reduce the footprint of these screenshot in my emails? I would rather avoid any manual intervention.

I suspect there may be a screen capture / clipboard utility that captures images in compressed form. That may work if anyone knows of a free one.