I'm trying to migrate from an expired trial version to the OSS version, but zmbackup -f -a all fails with:

Error occurred: invalid license

I'm not sure just how long ago the trial version expired, but would like to revert to the OSS version for now (I'm still hoping to convince some customers to sign up for the network edition).

Is there any way to do a backup before I try installing the OSS version? There's a fair bit of my personal mail in there that I don't want to lose

Regards,
Neill