One of the better open source newsletter managers that you will find these days is the one known as PHPLists which obviously (being open source) gives everybody the right to download it without having to pay anything for it, after which it can be installed and put to use and even be integrated easily with a website. In fact, the popularity of PHPLists can be judged from the fact that there are more than ten thousand downloads of this software each month and it is also considered as being among the best ten open source projects anywhere and it has been sponsored by tincan.
PHPLists can also be thought of as being a one-way delivery system for email announcement and it is well suited for newsletters, notifications as well as publicity lists and a lot more though it should not be confused with mailman which is another type of group mailing list system. You can even use PHPLists' web interface to write your own messages and to also send them and it is also possible to manage PHPLists via the Internet.
Other advantages to using PHPLists include its ability to keep on sending messages from the user's web server regardless of whether the user's computer is switched on or off and it also has vast capacity, having been designed to keep track of mailing lists which contain hundreds of thousands of other subscribers, though it is equally effective when used with small lists.
Another advantage to using PHPLists is that it makes use of a message queue and so you can be assured that it will deliver your email messages to each and every subscriber and also that there won't be any duplicate messages sent to a single subscriber, regardless of whether a subscriber has subscribed to multiple lists.
The list of advantages to using PHPLists is very long and so it is sufficient to say that it is certainly a most effective and useful software that you should well consider using.