spamdyke: rDNS File Format

# spamdyke

## A drop-in connection-time spam filter for qmail

## rDNS files

Some of spamdyke's options search files for rDNS names. In all those cases, the format of the files is the same. Blank lines and lines beginning with `#` are ignored. Every other line in the file is expected to contain a single entry.

NOTE: To protect against unknown dangers like programming errors, corrupted filesystems or incorrect file paths, spamdyke will only read the first 65536 lines of any file. If the file is any larger, spamdyke will printing an error message into its logs. If there is a legitimate reason to have more than 65536 lines in a file, the content should be separated into multiple files and spamdyke's option should be given multiple times to search each file.

Individual names may be given as separate entries. Those names will be matched literally. For example:

  `mail.example.com`
  `smtp.example.com`

Two names will be matched by these entries, `mail.example.com` and `smtp.example.com`.

The rDNS names may also use wildcards by beginning with dots (`.`) to match whole domains. For example, if the file contained the following entry:

  `.example.com`

The names `example.com`, `mail.example.com` and `mail.internal.example.com` will match. If the file contained the following entry:

  `.mail.example.com`

The names `mail.example.com` and `internal.mail.example.com` will match but `example.com` and `internal.example.com` will NOT.