Which mail server would you choose to develop your product on top of

Question

I am willing to build an email application which runs on the server side.

Not being familiar with any particular server I wonder if I can get some recommendations based on your experience.

I look for a stable, production ready and scalable daemon, which provide an easy-to-use c/cpp api interface.

I am willing to hook at the incoming and outgoing mails and manipulate them before shipment or placed in the inbox.

Note:

1. MS Exchange or any other not open-source are not an option
2. Must run on linux

Answer 1

Apache James is an open-source Java-based mail server with great options for extensibility.

Answer 2

Sendmail, as it has the advantage, that none of your (potential) customers can complain about it behaving in a nonstandard way - Sendmail is the de facto standard.

Of course everything else might be against it - but nobody in the world has a mail server which won't speak to sendmail.

I'm assuming of course here, that you want your mail server to be able to talk to other OEM mail servers, as this is pretty much a requirement of any such application.

If on the other hand, your mail server only needs to talk to other instances of itself (or other bespoke things you have control over and plan to test with), feel free to ignore this suggestion.