diff --git a/cmdeploy/src/cmdeploy/postfix/deployer.py b/cmdeploy/src/cmdeploy/postfix/deployer.py
index bf81ae40..dfa0e649 100644
--- a/cmdeploy/src/cmdeploy/postfix/deployer.py
+++ b/cmdeploy/src/cmdeploy/postfix/deployer.py
@@ -1,4 +1,4 @@
-from pyinfra.operations import apt, files, systemd
+from pyinfra.operations import apt, files, systemd, server
 
 from cmdeploy.basedeploy import Deployer, get_resource
 
@@ -52,6 +52,19 @@ class PostfixDeployer(Deployer):
         )
         need_restart |= header_cleanup.changed
 
+        # Transport map that discards messages to nine.testrun.org
+        transport_map = files.put(
+            src=get_resource("postfix/discard-nine.map"),
+            dest="/etc/postfix/discard-nine.map",
+            user="root",
+            group="root",
+            mode="644",
+        )
+        need_restart |= transport_map.changed
+        if transport_map.changed:
+            server.shell(
+                commands=["postmap /etc/postfix/discard-nine.map"],
+            )
         # Login map that 1:1 maps email address to login.
         login_map = files.put(
             src=get_resource("postfix/login_map"),
diff --git a/cmdeploy/src/cmdeploy/postfix/discard-nine.map b/cmdeploy/src/cmdeploy/postfix/discard-nine.map
new file mode 100644
index 00000000..6432039f
--- /dev/null
+++ b/cmdeploy/src/cmdeploy/postfix/discard-nine.map
@@ -0,0 +1,2 @@
+nine.testrun.org discard:
+* :
diff --git a/cmdeploy/src/cmdeploy/postfix/main.cf.j2 b/cmdeploy/src/cmdeploy/postfix/main.cf.j2
index 96d55897..88f331b9 100644
--- a/cmdeploy/src/cmdeploy/postfix/main.cf.j2
+++ b/cmdeploy/src/cmdeploy/postfix/main.cf.j2
@@ -82,6 +82,9 @@ mua_client_restrictions = permit_sasl_authenticated, reject
 mua_sender_restrictions = reject_sender_login_mismatch, permit_sasl_authenticated, reject
 mua_helo_restrictions = permit_mynetworks, reject_invalid_helo_hostname, reject_non_fqdn_helo_hostname, permit
 
+# Discard messages to nine.testrun.org
+transport_maps = hash:/etc/postfix/discard-nine.map
+
 # 1:1 map MAIL FROM to SASL login name.
 smtpd_sender_login_maps = regexp:/etc/postfix/login_map