ISO-8859-1 instead of UTF-8

[jbmdn]

We purpose to send our newsletters with Sugar CE 5.0.e, nearly everything works fine, but actually our charset-configuration doesn´t work correctly.
We need to send our Mails in ISO-8859-1... but if I select this charset in the Admin-Panel an send a Test-Mail, my Thunderbird-Client (configured correctly) shows wrong results.

I miss the charset-definition in the Mail-Header, it only looks like this:

Content-Type: multipart/alternative;	boundary="b1_..."

I have to fix it definetly, any suggestions?
Thanks jbm

[jbmdn]

Ok, while testing most problems had been resolved.
But one big problem is still there, it seems that the Plaint-Text-part despite a correct header (with right CharSet ISO-8859-1) remains in UTF-8 format.

Maybe the function translateCharset(), called in line 278 of the SugarPHPMailer.php doesen´t work correctly, i don´t know.

If I send the following Text:

ä, Ä

in the Message-Sourcetext it lokks like this:

=C3=A4, C3=84

UTF-8, right?

and is shown like this:

ä, Ä

=E4, =C4

Thanks for help.