Email Recipient List truncated using UTL_MAIL or UTL_SMTP

I have an issue where the email recipient list is getting truncated in OUTLOOK It just show 240 - 260 characters in the TO field whether I use UTL_MAIL or UTL_SMTP .It was all working fine till last month end.I am not sure must have changed.I tried putting my email and remaining 70+ fake emails to test,but it just shows 8 to 9 email in Outlook.

Although the email is being sent to all 80+ recipients as I did a test in lower environment.

I found the below reference but no solution

https://docs.microsoft.com/en-us/answers/questions/100041/email-recipieny-list.html

used code :

DECLARE
vemail VARCHAR2(4000);
BEGIN
  SELECT LISTAGG(email,';') WITHIN GROUP(ORDER BY email) INTO vemail FROM

 (SELECT 'raa@nyc.org' email FROM dual UNION
   SELECT 'raa'||LEVEL||'@nyc.org' FROM dual connect BY LEVEL < 80
 );
      utl_mail.send (sender      => 'test@nyc.org',
                          recipients   => vemail,
                          cc           => NULL,
                          bcc          => NULL,
                          subject      => 'TESTING',
                          message      => 'TESTING',
                          mime_type    => 'text/html; charset=us-ascii');

END;