If you have received a Posteo voucher code as a gift, you can either use it to open a new email account or add credit to your existing account.
When opening a new Posteo account, in the second step where you choose your payment method, simply choose “Voucher” and enter the code.
If you would like to add credit to your existing account with a Posteo voucher code, simply click “Settings” then “Vouchers” and then “Redeem a voucher using a voucher code”.
The value of the voucher will be added to your account straight away.