XamimeLT is an email scanner which encapsulates your existing sendmail or Postfix server setup. It scans both incoming and outgoing email. It can scan for email viruses, unwanted file types (eg. EXE, BMP, MPEG) and file names (eg. prettypark.exe), spam, and almost anything you care to search for in an email. It can also be used to scan for text snippets within emails and to insert disclaimers into outbound emails. XamimeLT was formerly known as "Inflex".
Heirloom mailx (formerly known as "nail") is derived from Berkeley Mail and provides the functionality of the System V and POSIX mailx commands. Additional features include support for MIME, IMAP (including caching and disconnected use), POP3, SMTP, S/MIME, international character sets, maildir folders, message threading, powerful search methods, scoring, and a Bayesian junk mail filter. Mailx can be used as a mail batch language in nearly the same way as it is used interactively. It can thus act as a mailbox filter, can fetch mail from remote accounts, and can send files as attachments.
aggregate takes a list of prefixes in conventional format on stdin, and performs two optimisations to reduce the length of the prefix list. It removes any supplied prefixes which are supurfluous because they are already included in another supplied prefix (e.g., 18.104.22.168/24 would be removed if 22.214.171.124/17 was also supplied), and identifies adjacent prefixes that can be combined under a single, shorter-length prefix (e.g., 126.96.36.199/24 and 188.8.131.52/24 can be combined into the single prefix 184.108.40.206/23).
JFetch is an application to download your email through protocols like POP3 and IMAP. The decision of whether to download a mail or not is made through a sequence of filters. By implementing certain interfaces, a user can very easily add his/her own filter to the current set of provided filters. Examples of filters are spam control, size restrictions, etc. JFetch downloads the email if it matches the criteria and then can deliver it using one of its delivery options.