This script converts an alias file to a sieve script for [stalwart-mail](https://stalw.art/).

## Usage
Given an alias file `testdata/simple.aliases` that contains lines of redirects of the form localpart with optional `@fqdn` followed by a space followed by a list (space or comma+space separated) list of destinations that consist of a localpart and optionally an `@fqdn`.
If you don't define a fqdn along any of the addresses, the default domain from your commandline input will be appended.

An example using the testdata directory of this repository:
```bash
$ ./alias_to_sieve testdata/simple.aliases example.com
```
```sieve
require ["variables", "copy", "vnd.stalwart.expressions", "envelope", "editheader"];

let "i" "0";
while "i < count(envelope.to)" {
  let "redirected" "false";
  if eval "eq_ignore_case(envelope.to[i], 'admin@example.com')" {
    addheader "Delivered-To" "admin@example.com";
    redirect :copy "me@example.org";

    deleteheader :index 1 :is "Delivered-To" "admin@example.com";
    let "redirected" "true";
  }
  if eval "eq_ignore_case(envelope.to[i], 'postmaster@example.com')" {
    addheader "Delivered-To" "postmaster@example.com";
    redirect :copy "me@example.org";

    deleteheader :index 1 :is "Delivered-To" "postmaster@example.com";
    let "redirected" "true";
  }
  if eval "eq_ignore_case(envelope.to[i], 'root@example.com')" {
    addheader "Delivered-To" "root@example.com";
    redirect :copy "me@example.org";

    deleteheader :index 1 :is "Delivered-To" "root@example.com";
    let "redirected" "true";
  }
  if eval "eq_ignore_case(envelope.to[i], 'sudo@example.com')" {
    addheader "Delivered-To" "sudo@example.com";
    redirect :copy "me@example.org";

    deleteheader :index 1 :is "Delivered-To" "sudo@example.com";
    let "redirected" "true";
  }
  if eval "!redirected" {
    let "destination" "envelope.to[i]";
    redirect :copy "${destination}";
  }
  let "i" "i+1";
}
discard;

```

If you have multiple domains with multiple alias files, pass them all in one run: `$ ./alias_to_sieve simple.aliases example.com other.aliases example.org`.

## Limitations
You cannot use apostrophes (') in any mail addresses although allowed by [RFC 5322](https://www.rfc-editor.org/rfc/rfc5322) since they would break termination of strings in sieve.

This parser is not designed with security in mind. While the above gives some basic protection against code injection, I have no idea whether sieve has other pitfalls that might allow them.

This is my first rust project, consume the code with care.

The generated code is specific to stalwart-mail and contains non-standard sieve features.