Is telus blocking RFC 3798 Message disposition notifications aka read receiptes on


I have a client using Outlook 2019 where any time he responds yes to sending a read receipt the message fails to send with SMTP error 452 4.1.0.


If I change his smtp server to a different provider the messages go through.


Because read receipts do not appear in the outbox they have to be manually removed from the mailbox or Outlook continues to attempt to send them in the background causing terrible mail delays.


Please advise.