Mail server software. Easy to use, professional technical support to help you answer questions, and one-time purchase, life-long free use, upgrade. It also has powerful background management functions, including subdomain management (managing a single domain independently) and superdomain management background (managing all domains). All of them have powerful functions such as user management, department management, mailing list management, address book management, announcement, operation log, welcome letter, custom domain name template, domain name signature, batch domain name addition, and mail monitoring management.