Special char shows up different on different Outlook account

Question

I have the following mail script in PHP:

$to = "my-mail-adress@test.se";
$subject = 'Test åäö';
$message = "Test åäö: ".$_REQUEST['test']."
                    <br><br>
                    Test åäö: ".$_REQUEST['test2']."
                    <br>
                    Test åäö: ".$_REQUEST['test3'];
$headers        = 'MIME-Version: 1.0' . "\r\n";
$headers        .= "Content-Type: text/html; charset=UTF-8\r\n";
$headers        .= "From: test@test.se \r\n";
mail($to,$subject,$message,$headers);

The document file is set to UTF-8 and also saved as "Encode in UTF-8 without BOM" in Notepad++.

When sending the mail to approximately four e-mail addresses that all gets opened in Microsoft Outlook 2010 everythings works fine and the chars åäöÅÄÖ is shown as åäöÅÄÖ. But on three other e-mail adresses that also opens their mail in Microsoft Outlook 2010 åäöÅÄÖ shows up as ö, Ã¥ and so on.

The mail provider says that the problem is in the encoding, which I have hard to believe when it works on four e-mail adresses out of seven.

How could this error occur? All the seven e-mail addresses are provied by the same supplier.

Answer 1

And are all the other three emails address which show the wrong format run on an Exchange Server? Ask the provider to provide this information. Also it would help to know if they are opening via the web client or not. As this could be an issue.