The command that manipulates mailboxes from CLI is zmmailbox. The following features are very usable:

• Place user account into maintenance mode. This will prevent delivery of new mail messages until we finish with the backup procedure:

  zmprov ma <user> zimbraAccountStatus maintenance
  

• Archive user's mailbox in tar.gz format:

  zmmailbox -z -m <user> getRestURL "//?fmt=tgz" > /tmp/<user>.tar.gz
  

• Empty Inbox folder:

  zmmailbox -z -m <sgros> ef /Inbox
  

• Restore user's mailbox from tar.gz format:

  zmmailbox -z -m <user> postRestURL "//?fmt=tgz&resolve=reset" /tmp/<user>.tgz

• Put user's account into active mode:

  zmprov ma <user> zimbraAccountStatus active