SPF is a new strategy for preventing junk mail. The present SMTP standard for email allows anyone to forge anyone else's email address. SPF verifies that the Sender address of an email message matches (according to some policy) the client IP address that submitted it. libspf2 is a complete and robust implementation of SPF which provides support for many MTAs. Support for new MTAs is in progress.
libsrs2 is the next generation SRS library. SPF verifies that the Sender address of an email message matches (according to some policy) the client IP address that submitted it. When a message is forwarded, the sender address must be rewritten to comply with SPF policy. The Sender Rewriting Scheme, or SRS, provides a standard for this rewriting that is not vulnerable to attacks by spammers, is easy to parse by common mail filters, and handles multiple hops neatly and safely.
mailprocd is a standalone mail classification and delivery daemon for massive multiuser servers, designed to extend the capabilities of MTAs such as Postfix and sendmail. It embeds perl in C in order to use SpamAssassin efficiently. It implements a process manager with persistent spam checker processes running under users' own UIDs.
mysqmail is a replacement for the qmail standard checkpasswd that performs authentication with a MySQL table. After authentication, it sets up two environment variables that it uses to perform traffic accounting. For SMTP, it provides an alternative logger for the qmail-send program. Instead of logs, it writes the traffic to a MySQL table for the related domain.
mysqmail-postfix-logger is a (very small) daemon that logs all SMTP traffic to an SQL database. It splits the information by domain and user for the From and To fields, making it very easy to count all the SMTP traffic for a given domain name. DTC (Domain Technologie Control) uses it for logging the SMTP traffic.
mysqmail-qmail-logger is a very small daemon that logs SMTP traffic such as successful delivery and relaying to an SQL database. It splits the information by domain and by users in both the to and from fields, which makes it very easy to count all the SMTP traffic for a given domain name.