Email Service provider should have the setup to send mass mails. There are many open source applications like Gmail, Exim and Postfix for this purpose. But these applications have its own limitations which restrict you from becoming a good email service provider.
– You can't have an IPS pool from where you can send emails randomly
– Cannot follow the throttling limit set by various ISPs
– No bounce processing mechanism
– Email authentication methods such as DK and DKIM are not flexible enough to apply
– Limit in the number of letters that can be sent
– Problems in using server resources correctly
All weaknesses above can be deleted if you will use paid mail service applications such as Ecelerity, Ironport, PowerMTA etc. will get you a good email service provider.
Because there is a strict competition now, because there are many providers you have to provide added value services such as campaign monitors where customers can find out how many of their letters have been sent to the inbox, bouncing etc.
The web interface must be clean and easy to navigate, you also have to have a strong technical support team that can constantly monitor services and ensure high shipping capabilities. High birth is closely related to the application you choose and most of the paid has the following advantages compared to open source email applications.