Mail Server Architecture

.Net application running on Mail server
This application is the one which processes the push mails. The mails pushed from the user end are first submitted in a mail filtering system which runs any site-defined mail filters to reject the message for all, or some recipients. The application is accessed through the interface provided at the admin end. The admin end web application can control the application through API of the same. The features of the .Net application can be listed as below:
SMTP/POP3 .Net email (32 & 64 bit) component library uses a simple API to send and receive mail, including HTML, MIME Base64 and quoted-printable encoded attachments, from within an application.
Features include:
- Send email with inline HTML, GIF, TIF, JPG, BMP and Rich Text attachments.
- Supports UTF-8 character coding.
- Get the number of messages on your email server (queue wise).
- Get the header lines from any email on your server without reading the entire email.
- Delete any email on the server without downloading the entire email.
- Copy any email on the server without deleting it.
- Receive any email on your server including MIME attachments.
- Download email from your server, automatically decoding MIME attachments.
- Remove contents of incoming attachments.
- Dozens of switches to control how email is sent and received.
- Run up to 128 independent threads concurrently.
- Supports SMTP (ESMTP) and POP3 authentication.
- Supports multiple (simultaneous) connections.
- Can work synchronously by allowing both incoming and outgoing mails at the same instance
- Supports bulk mail on a distribution list.
- Does not depend on support libraries. Makes calls to Windows API functions only.
- Can be used in the development of Win32 and Win64 applications.

The mail filtering and scheduling system will be developed in PHP and SOAP. After the user submitted job passes out of this filtering system, it gets placed in one of the mailing queues according to...