ExplorerTab.xml

<?xml version="1.0" encoding="UTF-8"?>
<customUI xmlns="http://schemas.microsoft.com/office/2009/07/customui" onLoad="ExplorerRibbon_Load">
  <ribbon>
    <tabs>
      <tab idMso="TabAddIns">
        <group id="MyGroup"
               label="Delay Send">
          <labelControl id="AutoDelaySendLabel" getLabel="AutoDelaySendLabel_getLabel"/>
          <checkBox id="DelaySend_OutOfOfficeMonday" label="Monday" onAction="outOfOfficeDayCheckBox_onAction" getPressed="outOfOfficeDayCheckBox_getPressed"/>
          <checkBox id="DelaySend_OutOfOfficeTuesday" label="Tuesday" onAction="outOfOfficeDayCheckBox_onAction" getPressed="outOfOfficeDayCheckBox_getPressed"/>
          <checkBox id="DelaySend_OutOfOfficeWednesday" label="Wednesday" onAction="outOfOfficeDayCheckBox_onAction" getPressed="outOfOfficeDayCheckBox_getPressed"/>
          <checkBox id="DelaySend_OutOfOfficeThursday" label="Thursday" onAction="outOfOfficeDayCheckBox_onAction" getPressed="outOfOfficeDayCheckBox_getPressed"/>
          <checkBox id="DelaySend_OutOfOfficeFriday" label="Friday" onAction="outOfOfficeDayCheckBox_onAction" getPressed="outOfOfficeDayCheckBox_getPressed"/>
          <checkBox id="DelaySend_OutOfOfficeSaturday" label="Saturday" onAction="outOfOfficeDayCheckBox_onAction" getPressed="outOfOfficeDayCheckBox_getPressed"/>
          <checkBox id="DelaySend_OutOfOfficeSunday" label="Sunday" onAction="outOfOfficeDayCheckBox_onAction" getPressed="outOfOfficeDayCheckBox_getPressed"/>
          <editBox id="DelaySend_StartBusinessHour" label="Start Work Hour" onChange="businessHourEditBox_onChange" getText="businessHourEditBox_getText"/>
          <editBox id="DelaySend_EndBusinessHour" label="End Work Hour" onChange="businessHourEditBox_onChange" getText="businessHourEditBox_getText"/>
        </group>
      </tab>
    </tabs>
  </ribbon>
</customUI>