Look at to implement undo send feature

src/CMakeLists.txt

@@ -175,6 +175,10 @@ set(kmailprivate_sieveimapinstanceinterface_LIB_SRCS
     sieveimapinterface/kmsieveimappasswordprovider.cpp
     )
 
+set(kmailprivate_undosend_LIB_SRCS
+    undosend/undosendcombobox.cpp
+    )
+
 set(kmail_common_SRCS)
 ecm_qt_declare_logging_category(kmail_common_SRCS HEADER kmail_debug.h IDENTIFIER KMAIL_LOG CATEGORY_NAME org.kde.pim.kmail)
 set(kmailprivate_LIB_SRCS
@@ -217,6 +221,7 @@ set(kmailprivate_LIB_SRCS
     ${kmailprivate_editor_plugininterface_LIB_SRCS}
     ${kmailprivate_checkindexing_LIB_SRCS}
     ${kmailprivate_sieveimapinstanceinterface_LIB_SRCS}
+    ${kmailprivate_undosend_LIB_SRCS}
     )
 
 qt5_add_dbus_adaptor(kmailprivate_LIB_SRCS

src/undosend/undosendcombobox.cpp

@@ -0,0 +1,32 @@
+/*
+   Copyright (C) 2019 Montel Laurent <montel@kde.org>
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; see the file COPYING.  If not, write to
+   the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02110-1301, USA.
+*/
+
+
+#include "undosendcombobox.h"
+
+UndoSendCombobox::UndoSendCombobox(QWidget *parent)
+    : QComboBox(parent)
+{
+
+}
+
+UndoSendCombobox::~UndoSendCombobox()
+{
+
+}

src/undosend/undosendcombobox.h

@@ -0,0 +1,33 @@
+/*
+   Copyright (C) 2019 Montel Laurent <montel@kde.org>
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public
+   License as published by the Free Software Foundation; either
+   version 2 of the License, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; see the file COPYING.  If not, write to
+   the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+   Boston, MA 02110-1301, USA.
+*/
+
+#ifndef UNDOSENDCOMBOBOX_H
+#define UNDOSENDCOMBOBOX_H
+
+#include <QComboBox>
+
+class UndoSendCombobox : public QComboBox
+{
+    Q_OBJECT
+public:
+    explicit UndoSendCombobox(QWidget *parent = nullptr);
+    ~UndoSendCombobox();
+};
+
+#endif // UNDOSENDCOMBOBOX_H