chasquid supports some functionality via hooks, which are binaries that get executed at specific points in time during delivery.

They are optional, and will be skipped if they don't exist.

Post-DATA hook

After completion of DATA, but before accepting the mail for queueing, chasquid will run the command at $config_dir/hooks/post-data.

The contents of the mail will be written to the command's stdin, and the environment is detailed below.

If the exit status is 0, chasquid will move forward processing the command, and its stdout should contain headers which will be added to contents of the email (at the top).

Otherwise, chasquid will respond with an error, and the last line of stdout will be passed back to the client as the error message. If the exit status is 20 the error code will be permanent, otherwise it will be temporary.

This hook can be used to block based on contents, for example to check for spam or virus. See etc/hooks/post-data for an example.


This hook will run as the chasquid user, so be careful about permissions and privileges.

The environment will contain the following variables:

There is a 1 minute timeout for hook execution. It will be run at the config directory.

Alias resolve hook

When an alias needs to be resolved, chasquid will run the command at $config_dir/hooks/alias-resolve (if the file exists).

The address to resolve will be passed as the single argument.

The output of the command will be parsed as if it was the right-hand side of the aliases configuration file (see Aliases for more details). Results are appended to the results of the file-based alias resolution.

If there is no alias for the address, the hook should just exit successfully without emitting any output.

There is a 5 second timeout for hook execution. If the hook exits with an error, including timeout, delivery will fail.