Maildrop is a powerful email filter/delivery agent. It supports mbox-style mailboxes and maildirs (a mail storage format used by Qmail). Its mail filtering language supports RFC822 parsing and GDBM/Berkeley DB database files. The maildrop package also includes a command-line tool to perform various operations on MIME messages.
GNU Anubis is an SMTP message submission daemon. It represents an intermediate layer between the mail user agent (MUA) and mail transport agent (MTA), receiving messages from the MUA, applying to them a set of predefined changes, and finally inserting modified messages into an MTA routing network. The set of changes applied to a message is configurable on a system-wide and per-user basis. The built-in configuration language used for defining sets of changes allows for considerable flexibility and is easily extensible.
GNU Mailutils is a rich and powerful protocol-independent mail framework. It contains a series of useful mail libraries, clients, and servers. These are the primary mail utilities for the GNU system. The central library is capable of handling electronic mail in various mailbox formats and protocols, both local and remote. Specifically, this project contains a POP3 server, an IMAP4 server, and a Sieve mail filter. It also provides a POSIX "mailx" client and a collection of other handy tools.
Redet is a tool for developing and executing regular expressions using any of more than 50 search programs, editors, and programming languages, intended both for developing regular expressions for use elsewhere and as a search tool in its own right. For each program in each locale, a palette showing the available constructs is provided. The properties of each program are determined by runtime tests, which guarantees that they will be correct for the program version and locale. Additional features include persistent history, extensive help, a variety of character entry tools, and the ability to change locale while running. Redet is highly configurable and fully supports Unicode.
Common Configuration Parser (CCP) is a program that reads configuration files and upgrades them. It takes an oldfile (typically the configuration file currently in use) and a newfile (typically the default new configuration file) and optionally a template (a file that describes how the generated configuration file should look) and merges the files into one, creating a new configuration file that has the changes made to the old file in addition to the new options included in the new file. It is completely independent of the program that created the configuration file, and can be used for many different purposes such as merging changes between an old user-edited configuration file and a .rpmnew file generated by RPM during upgrades.
Textmail filters a mail message or mbox, replacing MS Word, MS Excel, HTML, RTF, and PDF attachments with the plain text contained therein. By default, the following attachments are also deleted: image, audio, video, and MS Windows executables. MS winmail.dat attachments are replaced by any attachments contained therein, which are then replaced by text or deleted in the same fashion. Any of these actions can be suppressed with the command line options. Mail headers can also be selectively deleted.
GNU parallel is a shell tool for executing jobs in parallel locally or using remote computers. A job is typically a single command or a small script that has to be run for each of the lines in the input. The typical input is a list of files, a list of hosts, a list of users, a list of URLs, or a list of tables. If you use xargs today you will find GNU parallel very easy to use, as GNU parallel is written to have the same options as xargs. If you write loops in shell, you will find GNU parallel may be able to replace most of the loops and make them run faster by running several jobs in parallel. GNU parallel makes sure output from the commands is the same output as you would get had you run the commands sequentially. This makes it possible to use output from GNU parallel as input for other programs.
xtee (cross-tee/expanded tee) is a program for building complex pipelines. It resembles the tee command, except that instead of copying stdin to stdout, it copies an input file to stdout and stdin to an output file. You can use xtee for building things like a bidirectional HTTP filter (using netcat and sed).