HTML compliant

Could you explain a little more what you mean

He probably means that the emails are not sent in HTML, i was just about to make a post about it.

The messages are sent as one long string of plain text with no line-breaks and links are not clickable. When using it on my site, the received email is as follows:

"Personal Message: I found this great web site, which you should really check out! ---------------------- You are invited to check out MYSITE at http://www.mysite.com Sincerely, admin - admin@mysite.com

Very ugly and unprofessional looking, and the link to the site not being clickable is a huge problem

So is there a way to make the site link clickable before i uninstall this module??

Yes, there is, you can use html in the footer, something like:

<a href="!sitelink">!sitename</a>

I would also recommend using the mime mail module. (http://drupal.org/project/mimemail)
This module has an option which will enable html on *all* your email messages send by drupal and will give you some additional styling options.

However, tell-a-friend should offer some more options to customize the email. Currently, the linebreak (-----------) is not themeable/translatable as a string. See function tellafriend_page_submit();