i did exactly what u did, i bought my 8100 from telstra and using the optus network.
my phone came with .64 loaded, everything worked out of the box.
the optus zoo icon is a telstra one however.
i downloaded the optus .67 update. delete the vendor.xml from your computer HD.. and it will automagically ask u if u want to update your phone.. takes 10-15mins.... and everything works just as it should before...... telstra icon is still there however
edit - on the email topic... did optus give u the basic starter guide? its decent enough to get you going... www(dot)optus(dot)com(dot)au/blackberry ... set up and manage your account and off you go