After your turboSMTP account is activated (up to 24/48 hours after purchase) you can start sending emails using the "Standard Service", which does not require any advanced configuration.
Technically, it uses the "re-enveloping" technique.
The envelope sender address will be rewritten by the server to appear from turbo-smtp.com domain. For example, if the user is sending from "email@example.com" to "firstname.lastname@example.org", our servers will automatically change the envelope sender to VERP standard which looks like "email@example.com". This would cause the message to pass the SPF filter, because SPF check will be done for turbo-smtp.com not example.com.
Our servers will add a (Sender) header to message (for example, Sender: firstname.lastname@example.org) so that the message will pass the DomainKey/DKIM filters by verifying the key from our own DNS.
Users who choose the "Standard Service" do not even need to receive bounce messages as we will be handling that for them too. They can download a CSV file containing all bounced addresses from turboSMTP servers, or choose to receive their bounced messages. In that case, we will forward them.
All clients who are using the "Standard Service" can switch to the "White-labeled Service" (recommended) from their Client Area (Settings section), any time at no cost.
If you use the "Standard Service" your delivery rate may be lower: a full deliverability is ensured only using the White-labeled Service, and that is why we highly recommend to configure it.