Photoshop Social Media Icon Design Help?

[clctvsl32]

I'm making a social media icon for quick e-mail (I guess it's not totally social media, but that's beside the point). The image that I currently have is this: http://s16.postimage.org/5lmil91wh/mail_reg.png

As you can see, the @ sign is very rough. How can I make this icon where the @ sign is smooth? Please note that the space taken up by the @ and the background are transparent - only the gray/black circle area is solid color.

Any help is very much appreciated. Thanks.