Michel,
I have tried your steps but still the file that always get stuck during a backup is /CONF/MAIL/1.NOT.
I get the error when 1.NOT file is empty when I do not have a recipients assigned to the "migrated" Name. When I add a second Name and Recipient to the list which create another file called 2.NOT. Then I get the error during backup process.
However, if I go back to the "migrated" Name and assign a recipient e-mail address which makes 1.NOT not empty anymore. Then I can do backup without an error.
Conclusion: It seems like when 1.NOT (n.NOT) is empty or any empty file followed by another file, it gets stuck on the n.NOT file during a backup and it does not know how to go further to the next (n+1.NOT) file then it would error out. It does not matter if the n+1.NOT file is empty or not. As long as n.NOT file is empty and there is a n+1.NOT file, it errors. If n.NOT is empty and no n+1.NOT file exists, no error.
A bug?
bktong