- Plesk 12.5 for Linux
Always request a delivery status notification is not working when it is turned in RoundCube > Settings > Preferences > Composing Messages
QMail is in use
This is Plesk internal software issue with id #PPPM-4693 . The fix will be included in the next Plesk updates.
Switch from QMail to Postfix.
#213914225 How to define which MTA is used in Plesk and how to switch from QMail to Postfix and back