Can I export other than 72 dpi movie from AE ?

Martin' explanation is correct - but...

I like to use After Effects for batch output of images.

And since many systems use high resolution displays today, it would be nice to add a spatial resolution number to the output images. E.g. When working for a mailing, Outlook likes to have images with 96dpi. These are displayed better than the same image (with the same amount of pixels), saved as 72 dpi. 

So, it would be a nice extra when Ae could add a 'resolution' to image sequences, since some other apps use this number to decide how to display it. The 'resolution' is a part of the metadata of an image: A print analogy: Photoshop adds the spatial resolutio to its images as well, while InDesign can scale the images to whatever size (which make it hi or lo res in the end product. When checking for output, InDesign can warn for low resolution, because the intended resolution was enclose in the image file).

The same may apply for future applications of old low res movies next to new high res images and movies.

Thanks a lot guys! Very helpful. I must admit, it's the first time I supplied with this kind of odd pixel information from an outdoor media vendor. Thanks again for clarifying 🙂

As the others already said, it's utterly irrelevant for video. Video runs in absolute pixels.

Mylenium

I will try and make this simple. High-resolution images have a lot of pixels. The more pixels, the more data, the more data, the higher the resolution. Unfortunately, even people that teach in universities don't make this clear and use the wrong terms. Video, the web, mobile devices, all electronic devices that are capable of displaying images use pixels. You want high resolution, you supply more pixels. Here's a fun test that you can run. Download both of these images. They are exactly the same resolution - the same size. Drop them both in an app designed to print images like Word or In Design. One of them will be hard to see, the other will more than fill a page. The PPI metadata in an image file just tells the printer or the page layout program, how many pixels to print on an inch of paper.

I hope this helps you figure things out. There is no video standard that includes pixels per inch. 

There's no such settings. After effects only knows pixels. No ppi or dpi, only resolution.