[PHP] how to use HTML Symbol Entities with mail() ?

[cr.vegelin]

Hi List,

I am working on generated emails, using the mail() function.
Works fine, but when including characters like &#8743 (= ∧) or ∨ (= 
∨)
in the message, these characters are displayed as ? in the emails.

Snippet:
$headers  = 'MIME-Version: 1.0' . "\r\n";
$headers .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n";
...
$bool = mail ($mailto, $subject, $body, $headers);

also tested with:
$headers .= 'Content-type: text/html; charset=UTF-8' . "\r\n";
but without result.

Any ideas ?
TIA, Cor