How to detect mail client : desktop or mobile, and platform if mobile?

This question is similar to Standard way to dete开发者_运维问答ct mobile mail client? but not sure there's a solution inside. I understand how to handle mobile format with specific, screen-size-dependent css. But what about content AND/OR images ?

Case study :

- if mail is opened on desktop client app (Thunderbird,...) or web app (Gmail, ...), images say "download our iPhone app or Android app" with specific links to each app.

- if mail is opened on iOS, image says "get our iPhone app" with app store link.

- if mail is opened on Android, image says "get our Android app" with market link attached.

Is this even possible ? Are there tools to do it ? How would you proceed ?

Thanks !

You probably want some html tricks, but if this worked, such behavior would be most likely very dependent on email client used.

Various mail clients may display content rather differently. Some may show plain-text alternative, some may choose to display html form. Html rendering may also vary.

And no, there's no special filtering based on platform incorporated to email message format.

Some links about email message specifiaction: rfc 2822 rfc 2045