It is a separate e-mail sending service, which operates independent from any website. In case of our SMTP packages, the users get access to our SMTP service (an SMTP server address, a username, and a password), which can be set up - if their website supports its usage - and thus the letters will be sent through our SMTP service. It is also worth setting up an SPF record for the sender’s domain name, about whose setup our system sends detailed information.