We can therefore spare some lookups on the MDA, and use static:all
instead.

So our suffix is now a mere 'dc=fripost,dc=org'.  We're also using the
default '/var/lib/ldap' as olcDbDirectory (hence we don't clear it
before hand).

Which might be caused by slow LDAP lookups in transport_maps.  Instead,
we alias each addresses for which we want a custom transport to a
dedicated "dummy" domain, and use a static (CDB) transport_maps to map
said domains to their transport;  the receiver can then use canonical(8)
to restore the original envelope recipient.  Since the alias resolution
is performed by cleanup(8), which can run in parallel with other
instances, it should decongestion bottlenecks under heavy loads.

So far only the MX:es have been decongestioned.  The list manager and
the MDA should be treated as well.

That is, don't put a leading virtual_ or a trailing _maps in file names.

We introduce a limitation on the domain-aliases: they can't have
children (e.g., lists or users) any longer.

The whole alias resolution, including catch-alls and domain aliases, is
now done in 'virtual_alias_maps'. We stop the resolution by returning a
dummy alias A -> A for mailboxes, before trying the catch-all maps.

We're still using transport_maps for lists. If it turns out to be a
bottleneck due to the high-latency coming from LDAP maps, (and the fact
that there is a single qmgr(8) daemon), we could rewrite lists to a
dummy subdomain and use a static transport_maps instead:

  virtual_alias_maps:
    mylist@example.org -> mylist#example.org@mlmmj.localhost.localdomain

  transport_maps:
    mlmmj.localhost.localdomain mlmmj:

It has to be performed last, to give a chance to be accepted as a
regular mailbox.

We introduce a new, dedicated, smtpd daemon whose only purpose is to
resolve catch-alls.

Antispam & antivirus, using ClamAV and SpamAssassin through Amavisd-new.
Each user has his/her amavis preferences, and own Bayes filter (to
maximize privacy).

One question remains, though: how to set spamassassin's trusted_networks
/ internal_networks / msa_networks? It seems not obivious to get it
write with IPSec and dynamic IPs.
(Cf. https://wiki.apache.org/spamassassin/AwlWrongWay)

Other abreviations are upper case.