How to resize a video file in order to send it by email

Are you talking about a single picture or a moving picture? I'll assume it's a .jpg or .bmp or .png file or some similar snapshot.

I use Adobe Photoshop Elements, but you may not have that. Try opening the picture in Paint. Paint is on essentially every version of Windows.

In Paint, click "Image | Stretch/Skew". It lets you stretch (or shrink) the picture. To shrink the picture, enter a vertical and horizontal stretch of less than 100%. Also, in order to preserve the aspect ratio, make sure the vertical and horizontal percentages are equal.

Check out the following for information:

How to resize videos to 100mb for YouTube

How to resize video files for YouTube for free

Resizing videos software by WizeSoft and others