The main window of 1st SMTP Server allows you to access all the main features of the application. 

In the authentication tab of 1st SMTP Server you can choose how the users will be authenticated. 

The security module enables you to configure the anti distributed denial of service attack features. 

To further secure the SMTP server you can use IP filtering of the incoming connection's IP address. 

In the RBl servers window of 1st SMTP Server you can add to the list the srevres from which incoming connections will be automatically rejected. 

The SMTP options will enable you to further customize settings such as ports, connections and more. 

All the emails in the mailing system necessarily belong to a domain and here is where you can manage them all in 1st SMTP Server.