When setting up Mozilla Thunderbird 10 first you will be supported by an account wizard.
If you would like to add another eMail account later you'll have to call up the wizard manually. Click Tools > Account Settings > Account Actions > Add Mail Account... and the wizard will be started.
Please click the "Next" button.
Use the data for your eMail account from the EUserv customer center...
... and paste them into the Account Wizard...
By clicking on "Create Account" your EUserv eMail account has been successfullly set up in Thunderbird 10.