Marco -
If you are going to just use one account the best way is probably to
create a list for each customer. It would be possible to use a single
list, but all merge vars would likely have to be the same, signup our
public signup forms would have to be generic, and you'd need to waste
a segment condition for every campaign.
However, I would not suggest using one account - the best practice
would be to use a separate account for each customer. That way:
* there's never a chance of default account info appearing in a list
that's not fully configured
* you can give customer's access to the account as needed for reports
and other things you may not want to fully replicate
* if you ever need to, it's easy to let the customer take their
account and leave without much hassle
jesse