Sylpheed sometimes has problems showing national characters when viewing eg some Swedish newsletters.
I have tried different settings of "View" -> "Character encoding" like Auto detect, Unicode(UTF-8), Western European(ISO-8859-1) and others without success.
Here is a typical example:
Ett och annat guldkorn står att finna i det allt tätare nätet
This should read:
Ett och annat guldkorn st