It is flexible to the point where I would call it programming more than configuration. You can implement pretty much anything mail-related with it, including a mailing list. A good 15 years ago I used multiple Exim instances to implement a highly scalable regional mail service. (Microservices before they were called that.)
It's nice to see Haraka still being used, I did a fair bit of work with the predecessor "qpsmtpd" which was perl-based.
Moving to node.js at the time annoyed me, but it wasn't a bad choice at the time.
SMTP proxies still have their place, for protecting "real" servers from the hostile internet, and the plugin-nature of haraka/qpsmtpd allowed a lot of cute things to be done.
1. Very flexible configuration.
2. Can be linked with MySQL/other DBS to do queries for whatever informations and then derive delivery logic from that.
I've used extensively it in the era then ISPs/HSPs were providing email services.
> 1. Very flexible configuration. 2. Can be linked with MySQL/other DBS to do queries for whatever informations and then derive delivery logic from that.
Postfix can do this, and could do this, when I set up MySQL integration with postfix some 14 years ago.
GP was probably being tongue in cheek, but there is an argument that more cves means your product is more secure because it has been more finely examined.
Here however, I think its clear that postfix is the superior choice. It has been at least as finely examined and has stood the test of time.
Also find it interesting to see SMTP server like Haraka being used here and there (though it doesn't do local deliveries).
As a SMTP proxy, Postal is very convenient to see the flow of emails with good web UI.