diff --git a/comanage-registry-mailman/postfix/docker-postfix-entrypoint b/comanage-registry-mailman/postfix/docker-postfix-entrypoint
index 60a4c03..848e577 100755
--- a/comanage-registry-mailman/postfix/docker-postfix-entrypoint
+++ b/comanage-registry-mailman/postfix/docker-postfix-entrypoint
@@ -27,6 +27,7 @@ OUTPUT=/dev/stdout
 injectable_config_vars=( 
     POSTFIX_MYHOSTNAME
     POSTFIX_MYNETWORKS
+    POSTFIX_RELAYHOST
 )
 
 # If the file associated with a configuration variable is present then 
@@ -61,4 +62,8 @@ sed -i -e s@%%MYHOSTNAME%%@"${MYHOSTNAME}"@ /etc/postfix/main.cf
 MYNETWORKS=${POSTFIX_MYNETWORKS:-127.0.0.0/8 [::1]/128}
 sed -i -e s@%%MYNETWORKS%%@"${MYNETWORKS}"@ /etc/postfix/main.cf
 
+# Edit the postfix configuration file in place to set relayhost.
+RELAYHOST=${POSTFIX_RELAYHOST:-}
+sed -i -e s@%%RELAYHOST%%@"${RELAYHOST}"@ /etc/postfix/main.cf
+
 exec /usr/lib/postfix/sbin/master -c /etc/postfix -d
diff --git a/comanage-registry-mailman/postfix/main.cf b/comanage-registry-mailman/postfix/main.cf
index 0265ad5..7722558 100644
--- a/comanage-registry-mailman/postfix/main.cf
+++ b/comanage-registry-mailman/postfix/main.cf
@@ -60,7 +60,7 @@ myhostname = %%MYHOSTNAME%%
 alias_maps = hash:/etc/aliases
 alias_database = hash:/etc/aliases
 mydestination = $myhostname
-relayhost = 
+relayhost = %%RELAYHOST%%
 mynetworks = %%MYNETWORKS%%
 mailbox_size_limit = 0
 recipient_delimiter = +