## Deployment example There is nothing much in deploying mailserver to Kubernetes itself. The things are pretty same as in [`docker-compose.yml`][1], but with Kubernetes syntax. ```yaml apiVersion: v1 kind: Namespace metadata: name: mailserver --- kind: ConfigMap apiVersion: v1 metadata: name: mailserver.env.config namespace: mailserver labels: app: mailserver data: OVERRIDE_HOSTNAME: example.com ENABLE_FETCHMAIL: "0" FETCHMAIL_POLL: "120" ENABLE_SPAMASSASSIN: "0" ENABLE_CLAMAV: "0" ENABLE_FAIL2BAN: "0" ENABLE_POSTGREY: "0" ONE_DIR: "1" DMS_DEBUG: "0" --- kind: ConfigMap apiVersion: v1 metadata: name: mailserver.config namespace: mailserver labels: app: mailserver data: postfix-accounts.cf: | user1@example.com|{SHA512-CRYPT}$6$2YpW1nYtPBs2yLYS$z.5PGH1OEzsHHNhl3gJrc3D.YMZkvKw/vp.r5WIiwya6z7P/CQ9GDEJDr2G2V0cAfjDFeAQPUoopsuWPXLk3u1 postfix-virtual.cf: | alias1@example.com user1@dexample.com #dovecot.cf: | # service stats { # unix_listener stats-reader { # group = docker # mode = 0666 # } # unix_listener stats-writer { # group = docker # mode = 0666 # } # } SigningTable: | *@example.com mail._domainkey.example.com KeyTable: | mail._domainkey.example.com example.com:mail:/etc/opendkim/keys/example.com-mail.key TrustedHosts: | 127.0.0.1 localhost #user-patches.sh: | # #!/bin/bash #fetchmail.cf: | --- kind: Secret apiVersion: v1 metadata: name: mailserver.opendkim.keys namespace: mailserver labels: app: mailserver type: Opaque data: example.com-mail.key: 'base64-encoded-DKIM-key' --- kind: Service apiVersion: v1 metadata: name: mailserver namespace: mailserver labels: app: mailserver spec: selector: app: mailserver ports: - name: smtp port: 25 targetPort: smtp - name: smtp-secure port: 465 targetPort: smtp-secure - name: smtp-auth port: 587 targetPort: smtp-auth - name: imap port: 143 targetPort: imap - name: imap-secure port: 993 targetPort: imap-secure --- apiVersion: apps/v1 kind: Deployment metadata: name: mailserver namespace: mailserver spec: replicas: 1 selector: matchLabels: app: mailserver template: metadata: labels: app: mailserver role: mail tier: backend spec: #nodeSelector: # kubernetes.io/hostname: local.k8s #initContainers: #- name: init-myservice # image: busybox # command: ["/bin/sh", "-c", "cp /tmp/user-patches.sh /tmp/files"] # volumeMounts: # - name: config # subPath: user-patches.sh # mountPath: /tmp/user-patches.sh # readOnly: true # - name: tmp-files # mountPath: /tmp/files containers: - name: docker-mailserver image: tvial/docker-mailserver:latest imagePullPolicy: Always volumeMounts: - name: config subPath: postfix-accounts.cf mountPath: /tmp/docker-mailserver/postfix-accounts.cf readOnly: true #- name: config # subPath: postfix-main.cf # mountPath: /tmp/docker-mailserver/postfix-main.cf # readOnly: true - name: config subPath: postfix-virtual.cf mountPath: /tmp/docker-mailserver/postfix-virtual.cf readOnly: true - name: config subPath: fetchmail.cf mountPath: /tmp/docker-mailserver/fetchmail.cf readOnly: true - name: config subPath: dovecot.cf mountPath: /tmp/docker-mailserver/dovecot.cf readOnly: true #- name: config # subPath: user1.example.com.dovecot.sieve # mountPath: /tmp/docker-mailserver/user1@example.com.dovecot.sieve # readOnly: true #- name: tmp-files # subPath: user-patches.sh # mountPath: /tmp/docker-mailserver/user-patches.sh - name: config subPath: SigningTable mountPath: /tmp/docker-mailserver/opendkim/SigningTable readOnly: true - name: config subPath: KeyTable mountPath: /tmp/docker-mailserver/opendkim/KeyTable readOnly: true - name: config subPath: TrustedHosts mountPath: /tmp/docker-mailserver/opendkim/TrustedHosts readOnly: true - name: opendkim-keys mountPath: /tmp/docker-mailserver/opendkim/keys readOnly: true - name: data mountPath: /var/mail subPath: data - name: data mountPath: /var/mail-state subPath: state - name: data mountPath: /var/log/mail subPath: log ports: - name: smtp containerPort: 25 protocol: TCP - name: smtp-secure containerPort: 465 protocol: TCP - name: smtp-auth containerPort: 587 - name: imap containerPort: 143 protocol: TCP - name: imap-secure containerPort: 993 protocol: TCP envFrom: - configMapRef: name: mailserver.env.config volumes: - name: config configMap: name: mailserver.config - name: opendkim-keys secret: secretName: mailserver.opendkim.keys - name: data persistentVolumeClaim: claimName: mail-storage - name: tmp-files emptyDir: {} ``` __Note:__ Any sensitive data (keys, etc) should be deployed via [Secrets][50]. Other configuration just fits well into [ConfigMaps][51]. __Note:__ Make sure that [Pod][52] is [assigned][59] to specific [Node][53] in case you're using volume for data directly with `hostPath`. Otherwise Pod can be rescheduled on a different Node and previous data won't be found. Except the case when you're using some shared filesystem on your Nodes. ## Exposing to outside world The hard part with Kubernetes is to expose deployed mailserver to outside world. Kubernetes provides multiple ways for doing that. Each has its downsides and complexity. The major problem with exposing mailserver to outside world in Kubernetes is to [preserve real client IP][57]. Real client IP is required by mailserver for performing IP-based SPF checks and spam checks. Preserving real client IP is relatively [non-trivial in Kubernetes][57] and most exposing ways do not provide it. So, it's up to you to decide which exposing way suits better your needs in a price of complexity. If you do not require SPF checks for incoming mails you may disable them in [Postfix configuration][2] by dropping following line (which removes `check_policy_service unix:private/policyd-spf` option): ```yaml kind: ConfigMap apiVersion: v1 metadata: name: mailserver.config labels: app: mailserver data: postfix-main.cf: | smtpd_recipient_restrictions = permit_sasl_authenticated, permit_mynetworks, reject_unauth_destination, reject_unauth_pipelining, reject_invalid_helo_hostname, reject_non_fqdn_helo_hostname, reject_unknown_recipient_domain, reject_rbl_client zen.spamhaus.org, reject_rbl_client bl.spamcop.net # ... --- kind: Deployment apiVersion: extensions/v1beta1 metadata: name: mailserver # ... volumeMounts: - name: config subPath: postfix-main.cf mountPath: /tmp/docker-mailserver/postfix-main.cf readOnly: true # ... ``` ### External IPs Service The simplest way is to expose mailserver as a [Service][55] with [external IPs][56]. ```yaml kind: Service apiVersion: v1 metadata: name: mailserver labels: app: mailserver spec: selector: app: mailserver ports: - name: smtp port: 25 targetPort: smtp # ... externalIPs: - 80.11.12.10 ``` ##### Downsides - __Real client IP is not preserved__, so SPF check of incoming mail will fail. - Requirement to specify exposed IPs explicitly. ### Proxy port to Service The [Proxy Pod][58] helps to avoid necessity of specifying external IPs explicitly. This comes in price of complexity: you must deploy Proxy Pod on each [Node][53] you want to expose mailserver on. ##### Downsides - __Real client IP is not preserved__, so SPF check of incoming mail will fail. ### Bind to concrete Node and use host network The simplest way to preserve real client IP is to use `hostPort` and `hostNetwork: true` in the mailserver [Pod][52]. This comes in price of availability: you can talk to mailserver from outside world only via IPs of [Node][53] where mailserver is deployed. ```yaml kind: Deployment apiVersion: extensions/v1beta1 metadata: name: mailserver # ... spec: hostNetwork: true # ... containers: # ... ports: - name: smtp containerPort: 25 hostPort: 25 - name: smtp-auth containerPort: 587 hostPort: 587 - name: imap-secure containerPort: 993 hostPort: 993 # ... ``` ##### Downsides - Not possible to access mailserver via other cluster Nodes, only via the one mailserver deployed at. - Every Port within the Container is exposed on the Host side, regardless of what the `ports` section in the Configuration defines. ### Proxy port to Service via PROXY protocol This way is ideologically the same as [using Proxy Pod](#proxy-port-to-service), but instead of a separate proxy pod, you configure your ingress to proxy TCP traffic to the mailserver pod using the PROXY protocol, which preserves the real client IP. #### Configure your ingress With an [NGINX ingress controller][12], set `externalTrafficPolicy: Local` for its service, and add the following to the TCP services config map (as described [here][13]): ```yaml # ... 25: "mailserver/mailserver:25::PROXY" 465: "mailserver/mailserver:465::PROXY" 587: "mailserver/mailserver:587::PROXY" 993: "mailserver/mailserver:993::PROXY" # ... ``` With [HAProxy][11], the configuration should look similar to the above. If you know what it actually looks like, add an example here. :) #### Configure the mailserver Then, configure both [Postfix][2] and [Dovecot][3] to expect the PROXY protocol: ```yaml kind: ConfigMap apiVersion: v1 metadata: name: mailserver.config labels: app: mailserver data: postfix-main.cf: | postscreen_upstream_proxy_protocol = haproxy postfix-master.cf: | submission/inet/smtpd_upstream_proxy_protocol=haproxy smtps/inet/smtpd_upstream_proxy_protocol=haproxy dovecot.cf: | haproxy_trusted_networks = 10.0.0.0/8, 127.0.0.0/8 # Assuming your ingress controller is bound to 10.0.0.0/8 service imap-login { inet_listener imaps { haproxy = yes } } # ... --- kind: Deployment apiVersion: extensions/v1beta1 metadata: name: mailserver spec: template: spec: containers: - name: docker-mailserver volumeMounts: - name: config subPath: postfix-main.cf mountPath: /tmp/docker-mailserver/postfix-main.cf readOnly: true - name: config subPath: postfix-master.cf mountPath: /tmp/docker-mailserver/postfix-master.cf readOnly: true - name: config subPath: dovecot.cf mountPath: /tmp/docker-mailserver/dovecot.cf readOnly: true # ... ``` ##### Downsides - Not possible to access mailserver via inner cluster Kubernetes DNS, as PROXY protocol is required for incoming connections. ## Let's Encrypt certificates [Kube-Lego][10] may be used for a role of Let's Encrypt client. It works with Kubernetes [Ingress Resources][54] and automatically issues/manages certificates/keys for exposed services via Ingresses. ```yaml kind: Ingress apiVersion: extensions/v1beta1 metadata: name: mailserver labels: app: mailserver annotations: kubernetes.io/tls-acme: 'true' spec: rules: - host: example.com http: paths: - path: / backend: serviceName: default-backend servicePort: 80 tls: - secretName: mailserver.tls hosts: - example.com ``` Now, you can use Let's Encrypt cert and key from `mailserver.tls` [Secret][50] in your [Pod][52] spec. ```yaml # ... env: - name: SSL_TYPE value: 'manual' - name: SSL_CERT_PATH value: '/etc/ssl/mailserver/tls.crt' - name: SSL_KEY_PATH value: '/etc/ssl/mailserver/tls.key' # ... volumeMounts: - name: tls mountPath: /etc/ssl/mailserver readOnly: true # ... volumes: - name: tls secret: secretName: mailserver.tls # ... ``` [1]: https://github.com/tomav/docker-mailserver/blob/master/docker-compose.yml.dist [2]: https://github.com/tomav/docker-mailserver/wiki/Overwrite-Default-Postfix-Configuration [3]: https://github.com/tomav/docker-mailserver/wiki/Override-Default-Dovecot-Configuration [10]: https://github.com/jetstack/kube-lego [11]: https://hub.docker.com/_/haproxy [12]: https://kubernetes.github.io/ingress-nginx/ [13]: https://kubernetes.github.io/ingress-nginx/user-guide/exposing-tcp-udp-services/ [50]: https://kubernetes.io/docs/concepts/configuration/secret [51]: https://kubernetes.io/docs/tasks/configure-pod-container/configmap [52]: https://kubernetes.io/docs/concepts/workloads/pods/pod [53]: https://kubernetes.io/docs/concepts/architecture/nodes [54]: https://kubernetes.io/docs/concepts/services-networking/ingress [55]: https://kubernetes.io/docs/concepts/services-networking/service [56]: https://kubernetes.io/docs/concepts/services-networking/service/#external-ips [57]: https://kubernetes.io/docs/tutorials/services/source-ip [58]: https://github.com/kubernetes/contrib/tree/master/for-demos/proxy-to-service [59]: https://kubernetes.io/docs/concepts/configuration/assign-pod-node