# Which Problems Are Solved
#9185 changed that if a notification channel was not present,
notification workers would no longer retry to send the notification and
would also cancel in case Twilio would return a 4xx error.
However, this would not affect the "legacy" mode.
# How the Problems Are Solved
- Handle `CancelError` in legacy notifier as not failed (event).
# Additional Changes
None
# Additional Context
- relates to #9185
- requires back port to 2.66.x and 2.67.x
3fc68e5d60