I just spent 2 days investigation this issue. Our issue was that mailto: links on our utf-8 encoded web pages did not work for Outlook users if the subject= string contained non-ascii characters, like e.g Norwegian characters. An example is:
"mailto:[email protected]?subject=julegl?gg og f?rik?l"
From what I have learned so far, Outlook simply does not handle anything other than ASCII and iso-8859-1 characters. So when trying to click on the above mailto link (either from IE or Firefox), Outlook fails to decode the characters, leaving the subject broken and containing "weird" characters.
So the next step was to try to re-encode the pages in ISO-8859-1. What we did was to replace the original mailto link on the utf-8 page with a link to a "email-to-iso"-service, like this:
http://url.com/service.php?service=util.mailtoencode&mailto=mail%40coretrek.no%3Fsubject%3Demne+%C3%B8%C3%A6%C3%A5+emne
This page would convert the mailto characters to iso-8859-1 and then output the entire page content in iso-8859-1. A javascript on the page, containing "location.href='mailto:...'" was used to open the client's email client automatically.
So far everything seemed ok. This actually works in Internet Explorer, both with Thunderbird and Outlook (tested on IE7 on WinXP with Outlook express and TB 2).
BUT the problem now is actually Firefox. It seems like Firefox is unable to decode url-encoded urls containing characters found only in ISO-8859-1 but not in ASCII (like the norwegian ?, represented by %E5 when encoded). The same ? is handled correct if the page encoding is utf-8, but it seems like the Firefox developers have forgotten to test special characters together with the ISO-8859-1 charset.
The result is that Firefox passes an un-decoded string (still containing %E5 intstead of ?) to the email client. And, amazingly, this is handled correct by Outlook (which manages to decode the string itself), but NOT by Thunderbird, which probably has the same bug as Firefox. If you DON't url encode the subject, the string is passed correctly to Thunderbird, but not to Outlook.
We have also been trying other encoding methods, like php's htmlentities, htmlspecialchars, base64 encoding etc, but all of them fails one way or the other.
So, summarized:
Pages encoded in utf-8:
IE fails always
FF -> Thunderbird: OK
FF -> Outlook: FAIL
Pages encoded in iso-8859-1:
IE: OK
FF -> Thunderbird: Fails if subject is url encoded, ok if not)
FF -> Outlook: Fails if subject is not url encoded, ok if encoded)
(this is Windows, on Ubuntu Linux FF and TB works OK always).
Hoping this was helpful for others having the same problem.
