Regardingn FieldURI element UpdateItem SOAP request, getting error for Path variable while integrating with PEGA

Hi,

I am integrating PEGA with EWS and as a part of that using UpdateItem EWS Soap call.  This below input XML SOAP is working fine when I test with SOAP UI.

<soap:Envelope xxxxxx>
  <soap:Body>
     <m:UpdateItem MessageDisposition="SaveOnly" ConflictResolution="AlwaysOverwrite">
      <m:ItemChanges>
        <t:ItemChange>
          <t:ItemId Id="AAAAVrMXAAC=" ChangeKey="CQAAABYA"/>
          <t:Updates>
            <!--  AppendToItemField for appending instead of SetItemField -->
            <t:SetItemField>
              <t:FieldURI FieldURI="item:Subject" />
              <t:Message>
                <t:Subject>HI. TEST...Updated a Saveonly type email</t:Subject>
              </t:Message>
            </t:SetItemField>
          </t:Updates>
        </t:ItemChange>
      </m:ItemChanges>
    </m:UpdateItem>
  </soap:Body>
< /soap:Envelope>

While copying properties in to PEGA, I am getting issue with <t:FieldURI FieldURI="item:Subject" /> in the above request.  I couldn't find that property inside SetItemField.  Without that FieldURI value, when I do request in PEGA, I am getting this error.  I don't know what is path variable.  Can I get any help.

The request failed schema validation: The element 'SetItemField' in namespace 'http://schemas.microsoft.com/exchange/services/2006/types' has invalid child element 'Message' in namespace 'http://schemas.microsoft.com/exchange/services/2006/types'. List of possible elements expected: 'Path' in namespace 'http://schemas.microsoft.com/exchange/services/2006/types'.

Thank you.

KSVK