Support for Delivery Status Notification requests

[gwire]

I would be good if swaks could generate test DSN (RFC 3461) notification responses.

As a minimal feature, it would be useful to be able to request a response based on one or more of failure, delay, or success. eg

swaks --to example@example.com --dsn-notify=failure,delay,success

Then, if DSN is advertised after EHLO

<-  250-DSN

the RCPT TO: command has a NOTIFY= option appended to it.

 -> RCPT TO:<example@example.com> NOTIFY=FAILURE,DELAY,SUCCESS

[fm]

I would love this as well, I was about to email @jetmore to see if it was possible, until I found this issue

[georglauterbach]

Chiming in here as one of the core maintainers of docker-mailserver/docker-mailserver.

I am currently refactoring our test suite to move away from nc to swaks. For our DSN tests, this is required. Support for DSN would be awesome.

[polarathene]

Is --dsn-notify sufficient? Or is the request to only support a portion of the DSN extension? (NOTIFY parameter, which is what everyone here is interested in?)

• A library that implements support for this lettre (Rust) handles the RCPT command with support for multiple RCPT parameters.
• Looking at RFC 3461, there is more than just NOTIFY parameter for implementing the DSN extension.

---

Chiming in here as one of the core maintainers of docker-mailserver/docker-mailserver.

We now use swaks where possible. Thanks for such a great project, it really helped simplify our tests! 😁

For reference here is our test for DSN support (PR that introduced it) in docker-mailserver / DMS.

Reference

This is not necessary to know, but provides information/links regarding the test for better grokking what we're doing under the hood through convenience methods.

Collapsed as probably not relevant

The test presently handles sending these mails via netcat / nc (here is the _nc_wrapper() function):

_nc_wrapper 'emails/nc_raw/dsn/unauthenticated'
_nc_wrapper 'emails/nc_raw/dsn/authenticated' '0.0.0.0 465'
_nc_wrapper 'emails/nc_raw/dsn/authenticated' '0.0.0.0 587'

Where the two files referenced are [dsn/unauthenticated.txt](https://github.com/docker-mailserver/docker-mailserver/blob/25c7024cc4c7a6ee81be70144f6ecaf4fddf44ca/test/files/emails/nc_raw/dsn/unauthenticated.txt) and [dsn/authenticated.txt](https://github.com/docker-mailserver/docker-mailserver/blob/25c7024cc4c7a6ee81be70144f6ecaf4fddf44ca/test/files/emails/nc_raw/dsn/authenticated.txt).

We now have swaks used in most tests which is called via our _send_email() method.

Adapting test for swaks

Our _send_email() method will call swaks with some defaults, so the above _nc_wrapper snippet would only need to be changed to (or whatever equivalent --dsn-notify would use):

# Send a test mail to ports 25, 465, 587
_send_email --port 25 --dsn-notify=success,failure

_send_email --port 465 \
  --dsn-notify=success,failure \
  --auth-user user1@localhost.localdomain \
  --auth-password mypassword

_send_email --port 587 \
  --dsn-notify=success,failure \
  --auth-user user1@localhost.localdomain \
  --auth-password mypassword

To run the test, we have documentation here but is roughly:

# Requires these already installed: docker, jq, make, parallel

# Clone DMS repo and pull in the BATS testing submodule:
git clone --recurse-submodules --depth 1 https://github.com/docker-mailserver/docker-mailserver

# Run specific test (dsn.bats):
make clean generate-accounts test/dsn

Presently the Docker image will be built (Debian base) and installs swaks via the package manager in a shell script. You can modify that script file to add your unreleased swaks version, or if you're comfortable with Docker and only need to copy a local file into the image add a COPY instruction in the Dockerfile.

---

Testing with DMS

You seem to have your own test-suite but if it helps implement this feature more easily, DMS can quickly / easily provide a mail server for testing (Postfix, Dovecot, etc):

• Running with DSN configured (ports 465 and 587 offer it, port 25 disables by default).
• Just need docker installed.

# Run DMS:
# PERMIT_DOCKER=container relaxes some security checks (eg: DNS related)
docker run --rm -it -d \
  --hostname mail.example.test \
  --name dms \
  --env PERMIT_DOCKER=container \
  mailserver/docker-mailserver

# Add a user account:
docker exec -it dms setup email add hello@example.test bad-password

# For convenience, add your WIP swaks release into the running container:
docker cp /path/to/local/swaks dms:/path/in/container/swaks

# Run that copied over swaks within the container:
# NOTE: DMS defaults only enable DSN on submission(s) ports for authenticated users.
docker exec -it dms /path/in/container/swaks \
  --dsn-notify=success,failure \
  --protocol SSMTPA \
  --auth-user hello@example.test \
  --auth-password bad-password
  --server 0.0.0.0

# If you need shell access within the container just use:
docker exec -it dms bash

# When you're done bring the container down (--rm from `docker run` will handle cleanup):
docker stop dms

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We'll soon be adding a feature that would allow for testing #44 too if that interests you (SMTP Auth through Postfix delegates to Dovecot which handles XOAUTH support).