This patch moves the dovecot config from the container build to the helm
chart which allows to use templating with values that are configured at
runtime. This should provide more flexibility and standardizes the
dovecot container further.

This patch configures postfix to reject incoming email from its own
domains this is an effort to fight phishing of emails from my own domain
claiming to be from postmaster or alike.

References:
https://superuser.com/questions/964958/make-postfix-reject-incoming-email-spoofed-as-from-my-own-domain

Given that currently a lot of connections look broken and result quite delayed
mail delivery adjusting this interval will hopefully help to keep imap
connections alive and therefore delivering emails in realtime.

Currently for some reason postfix decided to drop all email that are
supposed to be relayed by default. This is obviously unwanted behaviour.
This patch takes the settings from the workaround.org project, applies
them to submission and submissions, which fixes the current issue.

However I still don't fully understand why.

References:
https://workaround.org/ispmail/bullseye/relay-outoing-email-through-postfix/

This patch switches the externalTrafficPolicy to `Local` for the
proxy-protocol enabled services, in order to skip kube-proxy when
connecting, this makes sure that proxy-protocol can actually function
and doesn't hit a node that would need to redirect traffic.

References:
https://metallb.org/usage/#layer2
https://github.com/kubernetes/kubernetes/issues/66607
https://github.com/digitalocean/digitalocean-cloud-controller-manager/pull/206

This patch disables error queries from zenhaus. It requires some more
tinkering down the line, but should accept email for now.

This patch allows to set the `HOSTNAME` variable, which should
explicitly set the hostname for the postfix pod and configure it to use
the proper external DNS name.

This patch fixes the absense of persistence for sieve rules, due to
being layed out in parallel to the `/srv/mail/mailbox` directory in the
dovecot container.

By moving the mountpoint to `/var/mail` the sieve rules should be
persisted along the way with the mailboxes.

BREAKING CHANGE: This patch adjusts the mount location for mail data,
which will require manual interaction.

Due to a copy-paste mistake, dovecot was using the postfix replicaCount
for its own. This is obviously not intended and was fixed by this
commit, correcting the snapshot and adding obviously needed tests to
prevent such a mistake in the future.

This patch deployes the fixed postfix image containg postscreen with
enabled smtpd.

This patch creates a PDB for postfix, if the setup is scaled to more
than 1 postfix replica. This way at least one postfix instance should
always be available and the MTA therefore HA.

Currently the dovecot backend is not yet HA, this should take place
later on.

This patch should enable the postfix setup in MoK to utilise the
proxy-protocol and therefore gather required IP information from
connecting clients.

It's implemented based on some documentation regard the topic and is
useful for reverse-proxy setups e.g. behind haproxy.

References:
https://www.haproxy.com/blog/efficient-smtp-relay-infrastructure-with-postfix-and-load-balancers/