change to our mailing-lists infrastructure

[Stoiko Ivanov <s.ivanov@proxmox.com>]

Hi,

We have migrated our mailing lists to mailman3.

Changes visible to you as subscribers:
1) the subject-prefix e.g. `[pve-devel]` was dropped - we recommend to
   use the `List-Id` header for matching, which has stayed consistent
   e.g. matching on `List-Id` contains `pve-devel.lists.proxmox.com`)
2) The footers with the mailing-list info link were dropped
3) No `Reply-To` header is set pointing to the list - use the Reply-All
   function of your mail-client
4) list-archives are now exclusively handled by https://lore.proxmox.com
   (existing links will continue to work)

points 1-3 were done in order to stop wrapping of some mails [0] due to the
DMARC policy of their sending domain.

The new web-interface can be found at:
https://lists.proxmox.com/postorius/lists/?all-lists

If you want to unsubscribe or change your subscription options, you'll
need to register an account first.

Kind Regards,
stoiko
for the mailing-list administration team

[1] https://docs.mailman3.org/projects/mailman/en/latest/src/mailman/handlers/docs/dmarc-mitigations.html