create or replace procedure sendMail(p_fromaddress IN VARCHAR2, --  Optional
                                               p_toaddress   IN VARCHAR2,
                                               p_bcc         IN VARCHAR2, --  Optional
                                               p_cc          IN VARCHAR2, --  Optional
                                               p_subject     IN VARCHAR2,
                                               p_contentType IN VARCHAR2, --  Optional
                                               p_msgbody     IN CLOB,
                                               p_appid       IN VARCHAR2,
                                               p_username    IN VARCHAR2,
                                               p_password    IN VARCHAR2,
                                               p_environment IN VARCHAR2, -- optional 'P' for Prod 'S' for Stggaing
                                               p_result      OUT VARCHAR2
                                               
                                               )

 is

  l_fromaddress    VARCHAR2(4000);
  l_plaindata      CLOB;
  l_subject        VARCHAR2(10000);
  l_toaddress      VARCHAR2(4000);
  l_contentType    VARCHAR2(1000);
  l_appid          VARCHAR2(50);
  l_username       VARCHAR2(50);
  l_password       VARCHAR2(50);
  l_bcc            VARCHAR2(2000);
  l_cc             VARCHAR2(2000);
  l_target_url     VARCHAR2(1000);
  l_error          VARCHAR2(500);
  l_correlation_id VARCHAR2(500);

  l_soap_request  CLOB;
  l_soap_response varchar2(32767);

  buffersize          NUMBER := 32000;
  chunk_buffer        VARCHAR2(32000);
  chunk_length        NUMBER;
  chunk_offset        NUMBER;
  request_body_length NUMBER;

  http_req  utl_http.req;
  http_resp utl_http.resp;
begin
  if p_contentType is NULL then
    l_contentType := 'text/plain;charset=UTF-8';
  else
    l_contentType := p_contentType;
  end if;

  l_fromaddress := p_fromaddress;
  l_plaindata   := p_msgbody;
  l_subject     := p_subject;
  l_toaddress   := p_toaddress;
  l_appid       := p_appid;
  l_username    := p_username;
  l_password    := p_password;
  l_bcc         := p_bcc;
  l_cc          := p_cc;

  if p_environment = 'P' then
    l_target_url := 'http://server1:8080/Process/PD-EmailNotifyService';
  else
    l_target_url := 'http://server2:8080/Process/PD-EmailNotifyService';
  end if;

  l_soap_request := '<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:mail="http://www.tibco.com/schemas/TibcoESB/CITP/MailMessage.xsd">
  <soap:Header/>
     <soap:Body>
      <mail:input_Mail_Type>
         <mail:Bcc>' || l_bcc || '</mail:Bcc>
         <mail:cc>' || l_cc || '</mail:cc>
         <mail:From>' || l_fromaddress ||
                    '</mail:From>
         <mail:plainData><![CDATA[' || l_plaindata ||
                    ']]></mail:plainData>
         <mail:subject>' || l_subject ||
                    '</mail:subject>
         <mail:To>' || l_toaddress ||
                    '</mail:To>
         <mail:contentType>' || l_contentType ||
                    '</mail:contentType>
         <mail:app_id>' || l_appid ||
                    '</mail:app_id>
         <mail:username>' || l_username ||
                    '</mail:username>
         <mail:password>' || l_password ||
                    '</mail:password>
      </mail:input_Mail_Type>
   </soap:Body>
 </soap:Envelope> ';

  -- DBMS_OUTPUT.put_line(l_soap_request);
  DBMS_OUTPUT.put_line(length(l_soap_request));

  http_req := utl_http.begin_request(l_target_url, 'POST', 'HTTP/1.1');

  utl_http.set_header(http_req, 'Content-Type', 'text/xml; charset=utf-8');
  -- added the below header to fix mail send 32kb issue
  utl_http.set_header(http_req, 'Transfer-Encoding', 'chunked');
  utl_http.set_header(http_req,
                      'SOAPAction',
                      '/CITP/Mail Notification/EmailNotifyService');
  -- added the below code to fix                       
  request_body_length := dbms_lob.getlength(l_soap_request);
  chunk_offset        := 1;
  while (chunk_offset < request_body_length) loop
    if chunk_offset + buffersize >= request_body_length then
      chunk_length := request_body_length - chunk_offset;
    else
      chunk_length := buffersize;
    end if;
    dbms_lob.read(l_soap_request, chunk_length, chunk_offset, chunk_buffer);
    
    utl_http.write_text(http_req, chunk_buffer);
    chunk_offset := chunk_offset + chunk_length;
    --DBMS_OUTPUT.put_line(chunk_buffer);
  end loop;
  -- utl_http.write_text(http_req, l_soap_request);
  -- the actual call to the service is made here
  http_resp := utl_http.get_response(http_req);
  
  [color=red]utl_http.read_text(http_resp, l_soap_response, 32767);[/color]
  utl_http.end_response(http_resp);  
 

  l_error := SYS.XMLTYPE.EXTRACT(xmltype(l_soap_response),'//ns0:error/text()','xmlns:ns0="' ||'http://www.tibco.com/schemas/TibcoESB/CITP/MailMessage.xsd' ||'"')
             .getstringval();

  p_result := SYS.XMLTYPE.EXTRACT(xmltype(l_soap_response),'//ns0:result/text()','xmlns:ns0="' ||'http://www.tibco.com/schemas/TibcoESB/CITP/MailMessage.xsd' ||'"')
              .getstringval();

  l_correlation_id := SYS.XMLTYPE.EXTRACT(xmltype(l_soap_response),'//ns0:correlation_id/text()','xmlns:ns0="' ||'http://www.tibco.com/schemas/TibcoESB/CITP/MailMessage.xsd' ||'"')
                      .getstringval();

  dbms_output.put_line(p_result || ' ' || l_error || ' ' ||
                       l_correlation_id);
  --p_result := l_soap_response;

EXCEPTION
  WHEN OTHERS THEN

    p_result := 'Exception  ' || chr(13) || SQLERRM;
end sendMail;

ORA-29266: end-of-body reached
 *Cause:  The end of the HTTP response body was reached.
 *Action: If the end of the HTTP response is reached prematurely, check if
          the HTTP response terminates prematurely.  Otherwise, end the
          HTTP response.

l_soap_response varchar2(32767);

l_soap_response clob;

Edit MC: Data removed at OP's request.