Explain why we use static transport maps and custom subdomains.

3 files changed, 34 insertions, 1 deletions

diff --git a/roles/IMAP/files/etc/postfix/transport b/roles/IMAP/files/etc/postfix/transport
index d40ac5d..94210e0 100644
--- a/roles/IMAP/files/etc/postfix/transport
+++ b/roles/IMAP/files/etc/postfix/transport
@@ -1 +1,17 @@
+# Each valid address user@example.org is aliased (on the MX) into some
+# example.org/user@xxx.fripost.org, and non-defaults next-hop:port are
+# chosen here in that table, depending on 'xxx'.  The reason for such
+# indirection is that there is only one qmgr(8) daemon, which delegate
+# the routing strategy to the trivial-rewrite(8), which in turns queries
+# transport_maps.  Hence high latency maps such as LDAP or SQL would
+# congestion the queue manager.  On the other hand, virtual aliasing is
+# performed by cleanup(8), multiples instances of which can run in
+# parallel. See http://www.postfix.org/ADDRESS_REWRITING_README.html .
+#
+# /!\ WARNING: xxx.fripost.org should NOT be in the list of valid
+# domains ($virtual_alias_domains)!  Otherwise at the next iteration of
+# the alias resolution loop the domain will be validated but not the
+# address, and the MTA will reply with "Recipient address rejected: User
+# unknown in virtual alias table".
+
 filter.mda.fripost.org  amavisfeed:[127.0.0.1]:10041
diff --git a/roles/MX/templates/etc/postfix/main.cf.j2 b/roles/MX/templates/etc/postfix/main.cf.j2
index e3b8ce0..22b68f3 100644
--- a/roles/MX/templates/etc/postfix/main.cf.j2
+++ b/roles/MX/templates/etc/postfix/main.cf.j2
@@ -55,7 +55,8 @@ relay_domains =
 # bottlenecks on trivial_rewrite(8) due to slow LDAP lookups in
 # tranport_maps.
 virtual_transport     = error:5.1.1 Virtual transport unavailable
-virtual_alias_domains = ldap:$config_directory/virtual/domains.cf
+virtual_alias_domains = !cdb:$config_directory/virtual/transport
+                        ldap:$config_directory/virtual/domains.cf
 virtual_alias_maps    = pcre:$config_directory/virtual/reserved_alias.pcre
                         # first we do the alias resolution...
                         ldap:$config_directory/virtual/alias.cf
diff --git a/roles/MX/templates/etc/postfix/virtual/transport.j2 b/roles/MX/templates/etc/postfix/virtual/transport.j2
index 9eac2be..57a0349 100644
--- a/roles/MX/templates/etc/postfix/virtual/transport.j2
+++ b/roles/MX/templates/etc/postfix/virtual/transport.j2
@@ -1,3 +1,19 @@
+# Each valid address user@example.org is aliased (on the MX) into some
+# example.org/user@xxx.fripost.org, and non-defaults next-hop:port are
+# chosen here in that table, depending on 'xxx'.  The reason for such
+# indirection is that there is only one qmgr(8) daemon, which delegate
+# the routing strategy to the trivial-rewrite(8), which in turns queries
+# transport_maps.  Hence high latency maps such as LDAP or SQL would
+# congestion the queue manager.  On the other hand, virtual aliasing is
+# performed by cleanup(8), multiples instances of which can run in
+# parallel. See http://www.postfix.org/ADDRESS_REWRITING_README.html .
+#
+# /!\ WARNING: xxx.fripost.org should NOT be in the list of valid
+# domains ($virtual_alias_domains)!  Otherwise at the next iteration of
+# the alias resolution loop the domain will be validated but not the
+# address, and the MTA will reply with "Recipient address rejected: User
+# unknown in virtual alias table".
+
 reserved.fripost.org    reserved-alias:
 
 {% if 'LDA' in group_names %}