Question: When creating links for an an html based email, how critical is it to use absolute links? Also, What are the benefits in using relative links in general?

Answer: 
For an html based email, absolute links are deal breaker critical, because they don't have the context of a web site to make relative links work. There are some mechanisms for setting the BASE of a document, but try feeding that to lotus notes...

Personally, on web sites, I try to use at least root absolute links /foo/yada.htm most of the time, because they are easier to test, and I never use parent path links unless putting something on a CD, like to have them turned off on the web server for security reasons. 

I work mainly with CMS/data driven sites, so don't have the pain of doing it by hand.
absolute links always start from the root website

```
/portal/images/myImage.png

```

relative links always start from the position of that page

```
../images/myImage.png

```

it is all about you when using this approaches, because I like to copy/past the hole web applications from server to server and sometimes place it in other sub folders, I tend to use Relative links more than absolute.

and in one domain root I always have several subfolders and some default files like:

* /webSite
* /portal
* /mail
* /iphone
* default.aspx
* robots.txt
* sitemap.xml

and inside everyone I have 

* /css
* /js
* /images
* files.aspx

instead of having a css in the root folder that contains all CSS files for all the sub applications for example, I always prefer to have all in just one place, it is better for me to move it somewhere else.

if you tend to build a web app to be permanent in that place, there is no warm to use absolute paths, it is a matter of taste and not best practice.

**HTML in the email** 

This is the place that you need to have the complete path 
 <http://www.mydomin.com/images/myImage.png>

hope it helps :)