The most impressive thing about courier mail server is that it has many features which are not available in other email servers like SPF, DMARC etc. It's free to use for small scale businesses as well as large ones.It also supports multiple languages such as English, French, Spanish, German etc. So if you want your business website or any of its pages to be accessible from all over the world then go with this software. I would say one can easily integrate the service into their own domain without much hassle. We have been using it since last 3 years and never faced any issue so far. As an organization we send out newsletters and promotional emails every month to our clients.This helps us reach more people across different countries.