Was that the exact command you used? .. or did you retype it for the comment?
... because I see a space between "Calendar/" and Peronal .. and your user's login is "username"? .. and it's a multi-domain setup with the target domain being "domain.tld"?
I'm going to assume this was not the actual command you used .. so -> did you confirm that the deleted folder exists on disk with the name you provided it?
Yes, I removed personal information and replaced it by generic values such as username, domain, etc. Sorry, I should have mentioned that. And yes, it's a multi-domain setup. The space between ...Calender/ Personal... came from formatting the post.
I run the command against the output of the list mailboxes command
So I guess the folder should be there. If I enter an invalid mailbox the I get the error below.