diff --git a/kmailIface.h b/kmailIface.h
index f7b5d45b0..14685c207 100644
--- a/kmailIface.h
+++ b/kmailIface.h
@@ -7,7 +7,6 @@
 #include <kurl.h>
 #include <qstringlist.h>
 //Added by qt3to4:
-#include <Q3CString>
 
 /** checkMail wont show reader but will check mail. use openReader to
     show if you give a filename to openReader it will show mbox or
@@ -43,25 +42,25 @@ k_dcop:
                             const QString &bcc, const QString &subject,
                             const QString &body, int hidden,
                             const QString &attachName,
-                            const Q3CString &attachCte,
-                            const Q3CString &attachData,
-                            const Q3CString &attachType,
-                            const Q3CString &attachSubType,
-                            const Q3CString &attachParamAttr,
+                            const QByteArray &attachCte,
+                            const QByteArray &attachData,
+                            const QByteArray &attachType,
+                            const QByteArray &attachSubType,
+                            const QByteArray &attachParamAttr,
                             const QString &attachParamValue,
-                            const Q3CString &attachContDisp) = 0;
+                            const QByteArray &attachContDisp) = 0;
   virtual int openComposer (const QString &to, const QString &cc,
                             const QString &bcc, const QString &subject,
                             const QString &body, int hidden,
                             const QString &attachName,
-                            const Q3CString &attachCte,
-                            const Q3CString &attachData,
-                            const Q3CString &attachType,
-                            const Q3CString &attachSubType,
-                            const Q3CString &attachParamAttr,
+                            const QByteArray &attachCte,
+                            const QByteArray &attachData,
+                            const QByteArray &attachType,
+                            const QByteArray &attachSubType,
+                            const QByteArray &attachParamAttr,
                             const QString &attachParamValue,
-                            const Q3CString &attachContDisp,
-                            const Q3CString &attachCharset) = 0;
+                            const QByteArray &attachContDisp,
+                            const QByteArray &attachCharset) = 0;
   /** Open composer and return reference to DCOP interface of composer window.
     If hidden is true, the window will not be shown. If you use that option,
     it's your responsibility to call the send() function of the composer in
diff --git a/kmkernel.cpp b/kmkernel.cpp
index 6f7325f13..081217c8a 100644
--- a/kmkernel.cpp
+++ b/kmkernel.cpp
@@ -28,7 +28,7 @@
 #include "undostack.h"
 #include "accountmanager.h"
 //Added by qt3to4:
-#include <Q3CString>
+#include <QByteArray>
 #include <QList>
 using KMail::AccountManager;
 #include <libkdepim/kfileio.h>
@@ -153,7 +153,7 @@ KMKernel::KMKernel (QObject *parent, const char *name) :
   // In the case of Japan. Japanese locale name is "eucjp" but
   // The Japanese mail systems normally used "iso-2022-jp" of locale name.
   // We want to change locale name from eucjp to iso-2022-jp at KMail only.
-  if ( Q3CString(QTextCodec::codecForLocale()->name()).toLower() == "eucjp" )
+  if ( QByteArray(QTextCodec::codecForLocale()->name()).toLower() == "eucjp" )
   {
     netCodec = QTextCodec::codecForName("jis7");
     // QTextCodec *cdc = QTextCodec::codecForName("jis7");
@@ -413,34 +413,34 @@ int KMKernel::openComposer (const QString &to, const QString &cc,
                             const QString &bcc, const QString &subject,
                             const QString &body, int hidden,
                             const QString &attachName,
-                            const Q3CString &attachCte,
-                            const Q3CString &attachData,
-                            const Q3CString &attachType,
-                            const Q3CString &attachSubType,
-                            const Q3CString &attachParamAttr,
+                            const QByteArray &attachCte,
+                            const QByteArray &attachData,
+                            const QByteArray &attachType,
+                            const QByteArray &attachSubType,
+                            const QByteArray &attachParamAttr,
                             const QString &attachParamValue,
-                            const Q3CString &attachContDisp )
+                            const QByteArray &attachContDisp )
 {
   kdDebug(5006) << "KMKernel::openComposer called (deprecated version)" << endl;
 
   return openComposer ( to, cc, bcc, subject, body, hidden,
                         attachName, attachCte, attachData,
                         attachType, attachSubType, attachParamAttr,
-                        attachParamValue, attachContDisp, Q3CString() );
+                        attachParamValue, attachContDisp, QByteArray() );
 }
 
 int KMKernel::openComposer (const QString &to, const QString &cc,
                             const QString &bcc, const QString &subject,
                             const QString &body, int hidden,
                             const QString &attachName,
-                            const Q3CString &attachCte,
-                            const Q3CString &attachData,
-                            const Q3CString &attachType,
-                            const Q3CString &attachSubType,
-                            const Q3CString &attachParamAttr,
+                            const QByteArray &attachCte,
+                            const QByteArray &attachData,
+                            const QByteArray &attachType,
+                            const QByteArray &attachSubType,
+                            const QByteArray &attachParamAttr,
                             const QString &attachParamValue,
-                            const Q3CString &attachContDisp,
-                            const Q3CString &attachCharset )
+                            const QByteArray &attachContDisp,
+                            const QByteArray &attachCharset )
 {
   kdDebug(5006) << "KMKernel::openComposer()" << endl;
 
diff --git a/kmkernel.h b/kmkernel.h
index 6650673be..c5b11c9d8 100644
--- a/kmkernel.h
+++ b/kmkernel.h
@@ -9,7 +9,7 @@
 //Added by qt3to4:
 #include <QLabel>
 #include <QList>
-#include <Q3CString>
+#include <QByteArray>
 //#include <weaver.h>
 //#include <weaverlogger.h>
 
@@ -121,26 +121,26 @@ public:
                     const QString &bcc, const QString &subject,
                     const QString &body, int hidden,
                     const QString &attachName,
-                    const Q3CString &attachCte,
-                    const Q3CString &attachData,
-                    const Q3CString &attachType,
-                    const Q3CString &attachSubType,
-                    const Q3CString &attachParamAttr,
+                    const QByteArray &attachCte,
+                    const QByteArray &attachData,
+                    const QByteArray &attachType,
+                    const QByteArray &attachSubType,
+                    const QByteArray &attachParamAttr,
                     const QString &attachParamValue,
-                    const Q3CString &attachContDisp);
+                    const QByteArray &attachContDisp);
 
   int openComposer (const QString &to, const QString &cc,
                     const QString &bcc, const QString &subject,
                     const QString &body, int hidden,
                     const QString &attachName,
-                    const Q3CString &attachCte,
-                    const Q3CString &attachData,
-                    const Q3CString &attachType,
-                    const Q3CString &attachSubType,
-                    const Q3CString &attachParamAttr,
+                    const QByteArray &attachCte,
+                    const QByteArray &attachData,
+                    const QByteArray &attachType,
+                    const QByteArray &attachSubType,
+                    const QByteArray &attachParamAttr,
                     const QString &attachParamValue,
-                    const Q3CString &attachContDisp,
-                    const Q3CString &attachCharset);
+                    const QByteArray &attachContDisp,
+                    const QByteArray &attachCharset);
 
   DCOPRef openComposer(const QString &to, const QString &cc,
                        const QString &bcc, const QString &subject,