More thank likely they sent you the thumbnail of the image and not the image itself. Without checking the top image size Imma gonna guess its around 300 x 240 ppi. Turns out it's about 320 x 240- which is typical thumbnail size.
Of course you can resample it- but what you get is a blurry image--- especially when your orignal image you are working with is small (in this case a thumbnail image) (which your OS creates automatically- and have standard sizes).
You need to use the original image, and not a thumbnail image. Ask them to send you the original file as an attachment.