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 has its own limitations which restricts you from becoming a good email service provider.
– You can not have a pool of ips from which you can send mails randomly
– Can not follow the throttling limit set by various ISP's
– No bounce processing mechanism
– Email authentication methods like DK and DKIM not flexible enough to implement
– Limitation in the number of mails that can be send
– Problems in using server resource correctly
All of the above drawbacks can be removed if you are going for paid mail service application like ecelerity, ironport, PowerMTA etc. These application along with an interface for users to create email template (HTML mail templates), auto-responders and schedule mail campaigns will make you a good email service provider.
Since there is a tight competition nowadays, as there are many providers you should provide value added service like campaign monitor through which customers can come to know how many of their mails has got delivered to inbox, bounced etc. The web interface should be clean and easy to navigate, also you should have a strong technical support team who can constantly monitor the service and ensure high deliverability. High deliverability is closely related with the application you have chosen and most of the paid ones have the following advantages over open-source mail applications.
– Lakh's of mails per hour
– Highly efficient in implementing email authentication methods like DK, DKIM etc
– IPWarmup methods helps in getting good IP reputation
– Can set throttling limits as per the rules of ISP's
– Effective Bounce mail processing methods
– Flexible filters so that you can decide what all mails should go out and what should not
– Efficient usage of server resource
– Graphical representation of email delivery status
– Pool of ips can allocated to your clients so that their mails are send out randomly from these ips.