I also use IRFANVIEW... it is a free download with no spam, etc. Have used it for years. For example, I can take a 3mg size and reduce it to 25 - 30% of its size and the final is just as sharp as the original. AND, just make sure you save the original of your photo..! There are some settings you have to do manually but everything is very easy.

This makes it great for emails, etc.

Highly recommended..!