MailWebForm allows you to send an email message from a Web site. It processes an HTML form, composes the email, optionally by processing a template, and delivers it. MailWebForm features spam protection in which the recipient's address is not specified in the HTML form, but rather uses property files to get the mail destination. Flexibility and ease-of-use are MailWebform's design goals. MailWebForm accepts three levels of parameter input: a global property file, user property files, and HTML form input. The setup is easily done through a administration Web site.
Coherent Mail Gateway is intended to be a very easy to set up MTA using SMTP and POP3. Greylisting is used on the SMTP daemon to reduce spam. In addition, quite a lot of checks on the validity of information from the SMTP client (such as claimed server name and sender) are carried out, and anyone caught telling lies is disconnected. Grey-, black-, and white-listing are supported, as well as (optionally) ClamAV and Spamhaus. The target market is users with static IP addresses. Others can use the system, but its value will be limited to outgoing email.
BackupMX consists of two programs, 'Store' and 'Forward'. Store accepts SMTP connections, takes all mail given to it, and stores it in a file. Forward takes that file and forwards it over SMTP to a fixed destination. This is code for integrating into your own projects rather than using as is. It is suitable for creating a disaster-recovery mail handler, but would also make a good basis for a spam filter, a tarpit, a honeypot, or a greylist filter. It is written in simple C, and has no external dependencies such as libsmtp.