qmail-spp 0.42

qmail-spp adds plugin support to qmails SMTP daemon (qmail-smtpd). qmail-spp is written entirely in C using native qmail libraries, so it does not create any dependencies.
qmail-spp has been written because currently there is no common way of enhancing qmail-smtpds functionality apart of patches which usually are not compatible one with other and require recompilation.
In addition, qmail-spp gives you possibility of enhancing your mail server in any language, so you can easily integrate it with anything you want.
Plugins are external programs which are executed after processing SMTP command, but just before accepting it by qmail; this lets you to add extra checks on commands arguments before accepting it; for instance you can check envelope recipient address against your "black list".
Plugins can be written in any language, because they are independent programs. They:
- should not read anything from standard input,
- should not exit with error code 120,
- should print all errors to standard error (they are logged),
- can print commands on standard output.