No, you do not need to purchase the paid Mailster versions every year. There is no problem with continuing to use your "old" installations/downloads - the limitations/restrictions only apply again, when you install a (free) release that was downloaded after your subscription period over your existing installation.
You can use Mailster on unlimited domains and installations. Furthermore you can keep on using the releases you got within one year after the subscription expired.
You can pay with PayPal or with credit card through the checkout process on our site. If you do not want to pay online we can offer you an offline payment via bank transfer to our account at a German bank. In that case please register at our site and send us a message including your details (full name, user name, address, company). We will then send you the invoice including the details of our bank account. After we receive the payment we will enable your username to access the member download section.
Although Mailster virtually runs on any hosting environments we recommend to check the system requirements from our documentation and, even better, to try out with the free Mailster version first before you decide to buy a premium version.
Yes, you can upgrade anytime no matter which product version you are on currently. Simply install the new version over your existing installation. You will keep all your existing mailing lists, users and emails. Although this should work without issues we always advise you to do a full backup of your site (database and files) first and then execute the installation/update process.
We have prepared a complete list of all features to compare the different Mailster product versions. If you still have questions feel free to contact us, we are happy to provide you with more information.