Hello,

I have modified questions as follows:

The communication via Internet should first of all be channelled by a
VPN-access (incl. Proxy; I use SecureSwiss). Afterwards it should be
channelled by the premium rate of JonDonym.

(a) Is it sufficient to start JonDonym after accessing the internet by
VPN in order to guarantee that the required effect occurs (so that all data will be sent via the VPN-access to the
entrance-mix of JonDonym)?
Or are special adjustments necessary?

(b) Will the complete data exchange (e.g. E-Mail, Updates, Chats,
etc.) be channelled via VPN and JonDonym considering the adjustments
mentioned in point (a)?

(c) Does it make any sense to use a Proxifier in order to deposit
JonDonym in it as a Proxy? Any internet access should also be
channelled first via VPN (incl. Proxy) and then via JonDonym.

2: You have to configure a proxy in JonDo and use your local Tor client. See: https://anonymous-proxy-servers.net/en/help/net.html (Compulsory proxy/firewall and Tor hints)

Open the configuration file "torrc" used by Vidalia with an text editor. You may find the file in the subdirectory "Data/Tor" of your TorBrowserBundle. Change the "SocksPort" from "auto" to a fixed value (usually port 9050).

# If non-zero, try to write to disk less frequently than we would otherwise.
AvoidDiskWrites 1
# Store working data, state, keys, and caches here.
DataDirectory .\Data\Tor
GeoIPFile .\Data\Tor\geoip
# Where to send logging messages. Format is minSeverity[-maxSeverity]
# (stderr|stdout|syslog|file FILENAME).
Log notice stdout
# Bind to this address to listen to connections from SOCKS-speaking
# applications.
SocksListenAddress 127.0.0.1

So, have I to create the entry "SocksPort 9050" ?

In connecting to jondo this way, the tor exit node sees only Jondo-encrypted traffic and the entry Jondo's mix sees only Tor exit nod's IP, right ?