Canon iR4570 Series Service Manual page 798

Cause
# 851
The remaining memory of the machine is
running short.
There are more than 100 files in the specified
box, not permitting additional storage.
# 852
The main power switch has been turned off
while a job is being executed, causing an error.
# 899
The transmission of e-mail or i-fax has ended.
However, the transmission has gone through
multiple servers, and there is no way of finding
out whether the transmission has reached the
target.
# 995
The reservation for the transmission has been
cancelled.
Remedy
Check the remaining memory of the machine;
then, remove unnecessary files for the Box.
Remove unnecessary files from the specified
box.
Check to see that the main power switch is on;
as necessary, try once again.
1. Check with the target to see if the
transmission has arrived.
2. Check to see if an error notice has arrived.
As necessary, start over.