With ZFS snapshot rollback the file system remains unchanged

Server with latest version available and ZFS File System.

I tried ZFS Snapshot. Below is the list of commands.

First I check if the zpool is available and create the snapshot.

At this point I copy a dozen emails and folders.

Then a rollback command I go back to email. If the rollback had worked the emails should have disappeared, instead the mail is still there.

Or am I wrong?

admin@srv1:~$ sudo zpool listNAME   SIZE  ALLOC   FREE  CKPOINT  EXPANDSZ   FRAG    CAP  DEDUP    HEALTH  ALTROOTzp0    444G  8.86G   435G        -         -     0%     1%  1.00x    ONLINE  -admin@srv1:~$ sudo zfs list -t snapshotno datasets availableadmin@srv1:~$ sudo zfs snapshot zp0@Testssadmin@srv1:~$ sudo zfs list -t snapshotNAME         USED  AVAIL     REFER  MOUNTPOINTzp0@Testss     0B      -       96K  -admin@srv1:~$ sudo zfs list -t snapshotNAME         USED  AVAIL     REFER  MOUNTPOINTzp0@Testss     0B      -       96K  -#### Send emailsadmin@srv1:~$ sudo zfs rollback zp0@Testss### Verified presence of emailsadmin@srv1:~$ sudo zfs list -t snapshotNAME         USED  AVAIL     REFER  MOUNTPOINTzp0@Testss     0B      -       96K  -admin@srv1:~$ sudo zfs destroy zp0@Testssadmin@srv1:~$ sudo zfs list -t snapshotno datasets available