Question: The question is to know if there is a way to build an HTML email with inline style (no CSS file, nor `<style>` tags) with the href links that react with the mouse passing over them : just to be able to change the color font.

So, no JS, no script, no `<style>`, just `<a href="http://www.dot.com style="....">link</a>`

Answer: 
The normal HTML way for inline styling is:

```
<a href="url" style="color:#cfe7fe";">Click me!</a>

```

But I am not sure how reliable that is in email templates.

You could always try: [(Although deprecated)](http://www.w3schools.com/html/html_fonts.asp)

```
<font color="blue"> <a href="url">Click me!</a> </font>

```

Hope it helps.

**Edit:** For inline hover try using:

```
onmouseover="this.style.color='blue';" 
onmouseout="this.style.color='black';"

```

But again I am not sure on email support for this.
Some E-Mail clients support `style` tags, and thus the defining of pseudo-selectors. According to this list:

[Guide to CSS support in E-Mail clients](http://www.campaignmonitor.com/css/)

`:hover` is supported by a good number of clients.

You should be able to slip a `<style>` tag into the body if necessary. That's not valid, but rich E-Mails are such a minefield that that is going to hardly matter.

`:hover` is your only chance I think. It's not possible to define pseudo-selectors inline, and JavaScript is out because it's going to be blocked by most (or all?) clients.