Below is the procedure used to send email from Oracle. This proc takes email content in varchar datatype or clob datatype.

CREATE OR REPLACE PROCEDURE myschema.send_email(
p_from in varchar2,
p_to in varchar2,
p_subject in varchar2,
p_text in varchar2 default null,
p_html in varchar2 default null,
p_smtp_hostname in varchar2,
l_clob_html IN CLOB DEFAULT NULL)
is
l_boundary varchar2(255) default 'a1b2c3d4e3f2g1';
l_connection utl_smtp.connection;
l_body_html clob := empty_clob; --This LOB will be the email message
l_offset number;
l_ammount number;
l_temp varchar2(32767) default null;
begin
l_connection := utl_smtp.open_connection( p_smtp_hostname);
utl_smtp.helo( l_connection, p_smtp_hostname );
utl_smtp.mail( l_connection, p_from );
utl_smtp.rcpt( l_connection, p_to );

l_temp := l_temp || 'MIME-Version: 1.0' || chr(13) || chr(10);
l_temp := l_temp || 'To: ' || p_to || chr(13) || chr(10);
l_temp := l_temp || 'From: ' || p_from || chr(13) || chr(10);
l_temp := l_temp || 'Subject: ' || p_subject || chr(13) || chr(10);
l_temp := l_temp || 'Reply-To: ' || p_from || chr(13) || chr(10);
l_temp := l_temp || 'Content-Type: multipart/alternative; boundary=' ||
chr(34) || l_boundary || chr(34) || chr(13) ||
chr(10);

----------------------------------------------------
-- Write the headers
dbms_lob.createtemporary( l_body_html, false, 10 );
dbms_lob.write(l_body_html,length(l_temp),1,l_temp);

----------------------------------------------------
-- Write the text boundary
l_offset := dbms_lob.getlength(l_body_html) + 1;
l_temp := '--' || l_boundary || chr(13)||chr(10);
l_temp := l_temp || 'content-type: text/plain; charset=us-ascii' ||
chr(13) || chr(10) || chr(13) || chr(10);
dbms_lob.write(l_body_html,length(l_temp),l_offset,l_temp);

----------------------------------------------------
-- Write the plain text portion of the email
if p_text is not null and p_text != ' ' then
l_offset := dbms_lob.getlength(l_body_html) + 1;
dbms_lob.write(l_body_html,length(p_text),l_offset,p_text);
end if;

----------------------------------------------------
-- Write the HTML boundary
l_temp := chr(13)||chr(10)||chr(13)||chr(10)||'--' || l_boundary ||
chr(13) || chr(10);
l_temp := l_temp || 'content-type: text/html;' ||
chr(13) || chr(10) || chr(13) || chr(10);
l_offset := dbms_lob.getlength(l_body_html) + 1;
dbms_lob.write(l_body_html,length(l_temp),l_offset,l_temp);

----------------------------------------------------
-- Write the HTML portion of the message

if p_html is not null and p_html != ' ' then
l_offset := dbms_lob.getlength(l_body_html) + 1;
dbms_lob.write(l_body_html,length(p_html),l_offset,p_html);
end if;

if l_clob_html is not null then
l_offset := DBMS_LOB.GETLENGTH(l_body_html) + 1;
DBMS_LOB.COPY(L_BODY_HTML, l_clob_html, DBMS_LOB.GETLENGTH(l_clob_html), L_OFFSET, 1);
end if;

----------------------------------------------------
-- Write the final html boundary
l_temp := chr(13) || chr(10) || '--' || l_boundary || '--' || chr(13);
l_offset := dbms_lob.getlength(l_body_html) + 1;
dbms_lob.write(l_body_html,length(l_temp),l_offset,l_temp);
--DBMS_OUTPUT.put_line (l_body_html);

----------------------------------------------------
-- Send the email in 1900 byte chunks to UTL_SMTP
l_offset := 1;
l_ammount := 1900;
utl_smtp.open_data(l_connection);
while l_offset < dbms_lob.getlength(l_body_html) loop
utl_smtp.write_data(l_connection,
dbms_lob.substr(l_body_html,l_ammount,l_offset));
l_offset := l_offset + l_ammount ;
l_ammount := least(1900,dbms_lob.getlength(l_body_html) - l_ammount);
end loop;
utl_smtp.close_data(l_connection);
utl_smtp.quit( l_connection );
dbms_lob.freetemporary(l_body_html);
commit;
end;
/

Happy Kooding… Hope this helps!