DKIM-Verify is a software application that can provide DKIM verification for non-DKIM-aware MDAs. Using DKIM-Verify, which functions as a "wrapper" for the MDA, mail originating from and destined for the local domain can be verified. In addition, DKIM-Verify can integrate with mailing list software to provide verification of messages received for later distribution.
SSA Fetchmail is a multi-threaded solution that retrieves new emails from ISP email accounts and forwards them through different channels like email, SMS, or a local SQL repository. It supports IMAP4, POP3, SSL, SMTP TLS delivery, SMPP SMS delivery, and local delivery. SSA Fetchmail supports thousands of email accounts provisioned in a MySQL database. Its performance is better than other solutions.
OpenSMTPD is an RFC compliant, secure, and simple SMTP server ported from OpenBSD to Linux. It supports the SMTP protocol, including SSL versions for added security, virtual domains, forward files, and external delivery agents like procmail, and can do most of the basic things that other MTA implementations do.
Clement is an email server application. Its main function is to block unwanted mail (spam) as soon as possible in the email exchange process. It accepts or rejects email while the SMTP session, initiated by the email sender, is still pending, accepting legitimate email messages without the need to return an error status to non-existent or "borrowed" return address later. Clement can operate in two modes. Either the mail is taken into account locally and stored in the recipient's own area, or it can transmit the mail to an another SMTP server (Sendmail, Postfix, Exim, Exchange, etc.). Each email domain name Clement knows about can be treated in one of these two modes depending on the group to which the domain name has been set. Each message is verified by a virus scanner (ClamAV) while the SMTP connection is still open, but the refusal of mail and the reason for refusal is notified to the actual sender. Mail management is done via a Web interface and can be delegated to three administrative levels (Root-Admin, Group-Admin, Domain-Admin). Standard users can access their own logs (sent email status, email rejected, quarantined email, etc.). With this interface, the user can handle the rejection and acceptance of mail. Users who are level "Admin" can access the session logs (via the Web interface). Clement uses a SQL database (PostgreSQL, MySQL) to store and manage logs, user profiles, and dynamic management of directives concerning the sender-receiver relationship.
Sendooway is a multi-user and multi-target ESMTP proxy that acts as mail transfer agent. Instead of configuring SMTP servers and authentication data for every mail identity on every device, it allows you to configure them centrally. Sendooway automatically uses the correct smarthost, logs on with the user's account data, and sends their mail.
Masqmail is an MTA (mail transport agent) for notebooks, workstations, home servers, and generally any host with no permanent network connection. It has special support for multiple transfer routes (e.g. to different mail providers). Address rewriting can be done in several ways. It is a slim replacement for full-blown MTAs such as sendmail, exim, qmail, or postfix and for the intended uses, configuration is much simpler.