Bulk Mailer helps speed the delivery of an email message to many recipients using Sendmail. It's best used in parallel with a mailing list manager such as Majordomo. For input, it takes a file of recipient addresses (one address per line) and a message (with headers already attached) to be sent to the recipients. It sorts the recipient list by reversed domain (so similar ones sort together), splits up the recipients into several groups containing no more than N domains each, creates an SMTP envelope for each group of recipients, and feeds each envelope to sendmail.
The Simple Mail Distributor is an Email::Filter-based Perl script which can be used to implement an administratively-managed mailing list. The service can be restricted to a list of allowed senders. Each message is sent individually with the To header adjusted to match the recipient.
pop3ml is a program to manage mailing lists and newsletters without a local SMTP server. It requires only a simple POP3 email account. It's highly configurable by users. You can subscribe or unsubscribe simply with email messages. There is optional subscription and unsubscription confirmation, subscription moderation, message moderation, digest message mode, parent/children list management, mail scheduling to postpone or repeat a message, a mail filter (with a procmail-like syntax), a message queue for unsent messages, message size check, a command to retrieve messages, bounce detection, message header management, black/white/allow/deny lists, and other functions. There is also a program to test list settings without sending any messages and another program to view and search through stored messages. You can configure it with programs like phpMyAdmin.
Listserv is software for managing mailing lists: creating lists, distributing emails over the list, adding new subscribers, and adjusting settings. It can be operated via a Web interface, by sending email commands, or via TCP. liblistserv is the glue between listserv and your C program for manipulating or querying a mailing list. By calling the provided functions, your program does not need to parse the results. Liblistserv is a reentrant library, written in C, meant for communication over TCP with a running Listserv instance.
mailing-lists-sieve is a utility to generate Sieve scripts (RFC 5228) for listserv mailing lists and upload them with the ManageSieve (RFC5804) protocol. The program can be extended to generate scripts for other mailing list managers or upload them by other means. mailing-lists-sieve can integrate into listserv and upload the scripts for the mailing lists when a new subscriber is added or removed from the list.
Sympa is a scalable and highly customizable mailing list software. It can cope with big lists (780,000 subscribers), and it comes with a complete Web interface for both the user and the administrator. It is internationalized. Sites can customize Web and mail templates, authentication backends, and authorization scenarios. Dynamic mailing lists can use multiple backends (LDAP, SQL, files, lists, or others). Sympa is the only S/MIME and DKIM enabled mailing list software, and it provides both authentication and encryption.