-o, --owner
          This  option  causes  rsync to set the owner of the destination file to be the same as the source file,
          but only if the receiving rsync is being run as the super-user (see also the --super  and  --fake-super
          options).   Without this option, the owner of new and/or transferred files are set to the invoking user
          on the receiving side.

          The preservation of ownership will associate matching names by default, but may fall back to using  the
          ID number in some circumstances (see also the --numeric-ids option for a full discussion).


   --numeric-ids
          With  this option rsync will transfer numeric group and user IDs rather than using user and group names
          and mapping them at both ends.

          By default rsync will use the username and groupname to determine what ownership  to  give  files.  The
          special  uid  0 and the special group 0 are never mapped via user/group names even if the --numeric-ids
          option is not specified.

          If a user or group has no name on the source system or it has no match on the destination system,  then
          the  numeric ID from the source system is used instead.  See also the comments on the "use chroot" set‐
          ting in the rsyncd.conf manpage for information on how the chroot setting affects  rsync’s  ability  to
          look up the names of the users and groups and what you can do about it.

sudo rsync -av --chown=vmail:vmail --force --delete --progress user@my_backup_server:/home/user/backups/vmail/ /vmail/