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https://github.com/martin-helmich/kube-mail
Policy-based SMTP daemon for sending emails from Kubernetes (experimental)
https://github.com/martin-helmich/kube-mail
Last synced: about 2 months ago
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Policy-based SMTP daemon for sending emails from Kubernetes (experimental)
- Host: GitHub
- URL: https://github.com/martin-helmich/kube-mail
- Owner: martin-helmich
- License: apache-2.0
- Created: 2018-06-21T15:24:44.000Z (over 6 years ago)
- Default Branch: master
- Last Pushed: 2024-02-29T13:09:34.000Z (7 months ago)
- Last Synced: 2024-07-02T15:41:36.593Z (3 months ago)
- Language: TypeScript
- Size: 1.4 MB
- Stars: 47
- Watchers: 5
- Forks: 9
- Open Issues: 12
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
- awesome - kube-mail - Policy-based SMTP daemon for sending emails from Kubernetes (experimental) (TypeScript)
README
# kube-mail -- SMTP server for Kubernetes
[](https://travis-ci.org/martin-helmich/kube-mail)
[](https://quay.io/repository/martinhelmich/kube-mail)
[](https://dependabot.com)
**:warning: CAUTION** This is entirely experimental and may eat your cluster.
kube-mail is a policy-based SMTP server designed for running in a Kubernetes cluster. It is configurable using Kubernetes Custom Resources and allows you to define policies for outgoing emails based on Pod labels (much like [NetworkPolicies](https://kubernetes.io/docs/concepts/services-networking/network-policies/)).
## Table of Contents
- [Installation](#installation)
- [Basic architecture](#basic-architecture)
- [Custom Resources](#custom-resources)
- [`SMTPServer` resources](#smtpserver-resources)
- [`EmailPolicy` resources](#emailpolicy-resources)
- [How-Tos](#how-tos)
- [Forward all emails from a Pod into a mail catcher](#forward-all-emails-from-a-pod-into-a-mail-catcher)
- [Sending mails from within a Pod](#sending-mails-from-within-a-pod)
- [PHP and ssmtp](#php-and-ssmtp)
- [Pending features](#pending-features)
## License
This project is licensed under the Apache-2.0 license.
Copyright 2023 Martin Helmich, Mittwald CM Service GmbH & Co. KG and [other contributors](https://github.com/martin-helmich/kube-mail/graphs/contributors).
## Installation
The helm chart of this controller can be found under [./deploy/helm-chart/kube-mail](./deploy/helm-chart/kube-mail).
Alternatively, you can use the [Mittwald Kubernetes Helm Charts](https://github.com/mittwald/helm-charts) repository:
```shell script
helm repo add mittwald https://helm.mittwald.de
helm repo update
helm install kube-mail mittwald/kube-mail --namespace kube-system
```
## Basic architecture
When installed, kube-mail acts as an SMTP server that Pods in your cluster can use to send outgoing mails. This server works without any of the typical SMTP authentication mechanisms; instead, the kube-mail SMTP server authenticates a Pod by its IP address and then tries to find a `EmailPolicy` resource that matches the source Pod (by label).
If an `EmailPolicy` has been found for a Pod, kube-mail will forward the email that should be sent to the upstream SMTP server configured in the `EmailPolicy`. If no `EmailPolicy` matches, kube-mail will reject the email.
Within your Pod, simply use `kube-mail..svc` as SMTP server without any authentication. kube-mail will do the rest.
## Custom Resources
This controller adds two Custom Resources to your Kubernetes cluster: A `SMTPServer` and a `EmailPolicy` resource, both from the `kube-mail.helmich.me/v1alpha1` API group.
### `SMTPServer` resources
An `SMTPServer` resource describes an SMTP server that should be used for outgoing mails. It is defined like follows:
```yaml
apiVersion: kube-mail.helmich.me/v1alpha1
kind: SMTPServer
metadata:
name: default
spec:
server: smtp.yourserver.example
port: 465
tls: true
authType: PLAIN
```
Concerning the individual properties:
.spec.server- The host name of your upstream SMTP server. This may be either an external service, or a cluster-internal service (for example, specified by its
.svc.cluster.localaddress) .spec.port- The port that the upstream SMTP server is listening on. If omitted, 587 is assumed as default.
.spec.tls- Defines if the upstream server uses TLS.
.spec.authType- The SMTP authentation type. Supported values are
PLAIN,LOGIN,CRAM-MD5andSCRAM-SHA-1.
### `EmailPolicy` resources
An `EmailPolicy` defines what kube-mail should do with mails received from a certain pod. An email policy will forward the received email to one of the SMTP servers configured using the `SMTPServer` resources.
A forwarding email policy is defined like follows:
```yaml
apiVersion: kube-mail.helmich.me/v1alpha1
kind: EmailPolicy
metadata:
name: my-policy
spec:
podSelector:
matchLabels:
app.kubernetes.io/name: my-name
ratelimiting:
maximum: 100
period: hour
sink:
smtp:
server:
name: default
namespace: default
credentials:
name: default-credentials
namespace: default
```
Concerning the individual properties:
.spec.podSelector- This is a selector for the Pods this EmailPolicy should apply to. When a SMTP connection is opened to kube-mail, it will identity the source Pod by its Pod IP address and then test if the source Pod matches this label selector.
.spec.ratelimiting- Rate limiting may be configured per Policy. Allowed periods are
"hour"and"minute". Messages are counted per policy, not per Pod. .spec.sink-
sinkdescribes where kube-mail should deliver received emails. This may either be an SMTP server (described by aSMTPServerresource) or kube-mail's internal database.
.spec.sink.smtp.server-
serveris a reference to aSMTPServerresource. It may be placed in a different namespace. .spec.sink.smtp.credentials-
credentialsis a reference to aSecretresource with a"username"and"password"key. It may be placed in a different namespace. NOTE: If omitted, kube-mail will attempt an unauthenticated connection to the SMTP server.
## How-Tos
### Forward all emails from a Pod into a mail catcher
Forwarding all outgoing emails into a mail catcher (like [MailHog](https://github.com/mailhog/MailHog)) is a common use case in development environments, where an application should not be allowed to actually send emails out into the world. To configure kube-mail to forward all emails into a mail catcher, proceed as follows.
1. Make sure that kube-mail is up and running in a namespace of your choice (for this example, we'll assume that kube-mail is running in the `kube-system` namespace).
1. Install the mail catcher of your choice. MailHog, for example, has a [Helm chart](https://github.com/codecentric/helm-charts/tree/master/charts/mailhog) that makes it easy to install:
```
$ helm repo add codecentric https://codecentric.github.io/helm-charts
$ helm install \
--namespace kube-system \
--name mailhog \
codecentric/mailhog
```
1. Configure an `SMTPServer` resource pointing to your MailHog service:
```yaml
apiVersion: kube-mail.helmich.me/v1alpha1
kind: SMTPServer
metadata:
name: mailhog
namespace: kube-system
spec:
server: mailhog.kubemail-system.svc.cluster.local
port: 1025
tls: false
```
1. Configure an `EmailPolicy` to catch emails from a Pod and forward them to the configured `SMTPServer`. The policy resource needs to be in the same namespace as the Pod that's sending mails.
```yaml
apiVersion: kube-mail.helmich.me/v1alpha1
kind: EmailPolicy
metadata:
name: pod-to-mailhog
namespace: default # needs to be same namespace as Pod
spec:
podSelector:
matchLabels:
app.kubernetes.io/name: my-name
sink:
smtp:
server: # server may be in a different namespace than policy
name: mailhog
namespace: kube-system
```
## Sending mails from within a Pod
### PHP and ssmtp
Provide `ssmtp` in your Pod; use the following configuration (`/etc/ssmtp/ssmtp.conf`):
```
mailhub=kube-mail.kube-system.svc.cluster.local
hostname=foo
FromLineOverride=yes
```
Then in the php.ini:
```
sendmail_path = /usr/sbin/ssmtp -t
```
## Pending features
- [ ] Rate limiting
- [ ] TLS for cluster-internal communication