I also use Sendy: one with Amazon SES and one with a more dodgy local Postfix server. I am quite happy with it, but the feature missing in sendy is Segmentation. How does this compare?

Mailtrain allows you to create segments over exact or relative matches eg. "all users where signup date is after 7 days before today" or "users who have custom numeric field value between 1 and 10". There's not too much documentation about it but you an find some from the Wiki https://github.com/andris9/mailtrain/wiki/Relative-date-rang...

Do yourself a favor and read the Sendy source code.

Can you elaborate?

Here's one example of what I saw.

Imagine you want to track every open and every click an email gets. Most of the email clients nowadays block that hidden image that is used to track openings. So, if a user clicks on a link, that obviously means that they opened the email and an email open should be tracked as well.

In order to do that, one might write a function that tracks opens and call that on the tracking pixel and whenever a link in clicked.

Well, that's not what happens on that software. When the, for instance, `linktracker.php` runs, it makes a HTTP request (think open('http://$HOST:$PORT/opentracker.php?uid=$UID&campaign=$campai...) ) to the `opentracker.php`, simulating what a browser would do, in order to avoid duplicating the code.

I read on multiple places that it's a total mess, probably he means that :p