How does email work?

Question

While I haven't used it, an email web application called Litmus

Answer 1

Here is my best guess. Since this link is published in rockinthesixstring, it uses images, but not javascript.

How long has someone read the letter.

Put several images in an email, which takes some time to download, if the letter is read for a long time, more are downloaded.

Will it be sent.

Is an image loaded from multiple IP / User agents?

Is it deleted.

Screenshots show this in conjunction with a look.

Is it printed.

Add a background image error to the print style sheet. A.

What email client was used to read it.

Check user agent.

Answer 2

Any email app I've seen uses an image tracker. Basically, if you attach the generated 1x1 px image code somewhere in the email, then while loading this image on the server side you capture all ServerVariables

http://msdn.microsoft.com/en-us/library/ms524602%28VS.90%29.aspx

EDIT:

I just read some information on the Litmus website and it looks like it confirms what I wrote above regarding image tracking