I'm new on this video thing, any help appreciated!

Here's my scenario. I'm preparing several short vids to embed in powerpoint files. I imported the files with max quality. The size is 530x360, and length varies, from 250frames to 500frames.

The problem is, on the lengthier vids, I'm getting 21mB files, and ideally would like 5mb and under. (our email is limited to 5mb). Once the video is imported, is it possible to compress on export, or does the compression have to happen on import only? I tried the jpeg quality slider under Publish Settings, but this had no result (I guess that only works on images)