commit 6d80788587894ee0cf3e087f959226a3d764af95
Author: Thomas McGuire <mcguire@kde.org>
Date:   Sat Apr 16 21:56:01 2011 +0100

    Use UTF-8 if the charset can't encode the string.
    
    Hopefully the call to canEncode() won't affect the performance too
    much...
    
    BUG: 263761
    (cherry picked from commit 7b75f8a769ef0e40e59dedb1327ff0ed51e63ba9)

diff --git a/kmime/kmime_util.cpp b/kmime/kmime_util.cpp
index 29ea676..ab1906c 100644
--- a/kmime/kmime_util.cpp
+++ b/kmime/kmime_util.cpp
@@ -287,6 +287,11 @@ QByteArray encodeRFC2047String( const QString &src, const QByteArray &charset,
       usedCS = charset;
   }
 
+  if ( !codec->canEncode( src ) ) {
+    usedCS = "utf-8";
+    codec = QTextCodec::codecForName( usedCS );
+  }
+
   if ( usedCS.contains( "8859-" ) ) { // use "B"-Encoding for non iso-8859-x charsets
     useQEncoding = true;
   }
diff --git a/kmime/kmime_util.h b/kmime/kmime_util.h
index 84c061e..ebe2a38 100644
--- a/kmime/kmime_util.h
+++ b/kmime/kmime_util.h
@@ -165,7 +165,7 @@ KMIME_EXPORT extern QString decodeRFC2047String( const QByteArray &src );
   Encodes string @p src according to RFC2047 using charset @p charset.
 
   @param src           source string.
-  @param charset       charset to use.
+  @param charset       charset to use. If it can't encode the string, UTF-8 will be used instead.
   @param addressHeader if this flag is true, all special chars
                        like <,>,[,],... will be encoded, too.
   @param allow8bitHeaders if this flag is true, 8Bit headers are allowed.