AMaViS (A Mail Virus Scanner) scans e-mail attachments for viruses using third-party virus scanners available for UNIX environments. It resides on a UNIX (Linux) machine and looks through the attached files arriving via e-mail, generates reports when a virus is found and sets the delivery on hold.
Approver is a set of scripts for automatically approving posts to Majordomo-moderated mailing lists based on the sender's email address. Approver also converts HTML email posts to plain text by first filtering them through DEMIME, and it bounces all posts submitted to mailing lists made by non-list members, preventing list moderators from being bombarded by bogus submissions created by email worms and viruses originating from list member's infected computers.
AqMail fetches mails from remote mailboxes (POP3), applies admin-defined filters, and stores the email in local mailboxes for POP3 daemons to serve them. It supports virtual mail domains and users. It has been tested with QMail as the MTA and with Spamassassin and ClamAV as filters.
Arb-Scan is a remote banner scanner written in bash and Perl. It supports 12 different services banner checks (daytime, ftpd, sshd, smtpd, domain, finger, httpd, pop2, pop3, nntp, imapd and snpp). It features IP file reading, logging, random IP scanning, ftp anonymous login checking and VRFY/EXPN smtp checking.
Deliver Maildir is a tool that delivers messages from STDIN to a Maildir format mail directory with support for committing or rolling back the delivery. The commit/rollback instruction is accomplished by sending signals to the process. It also contains example code for using it from various scripting languages.
Hitchhiker's Guide to the Internet is a German introduction to the technical aspects of the Internet. This book explains both the low-level protocols IP, ICMP, TCP, and UDP and the high-level protocols SMTP, POP3, IMAP4, NNTP, HTTP, Gopher, FTP, IRC, DICT, Finger, Daytime, DNS, and Whois.