HTTP is not redirected to HTTPS on my server. I tried switching back and forth and the error was always the same. One difference with my issue than the original poster is that I'm also getting the error from the brower.
From the command line:
/opt/zimbra/bin/zmmailbox -z -m
user@hostname.domain.com getRestURL "//?fmt=tgz" > /backup/accounts/user.tgz
ERROR: service.FAILURE (system failure: GET failed, status=501 not implemented yet)
From a web browser login as the user and go to
http://server.domain.com/home/user/?fmt=tgz
but I basically get the same error:
HTTP ERROR: 501
not implemented yet
RequestURI=/service/home/user/