diff --git a/debian/ai-auth-server.conf b/debian/ai-auth-server.conf
index b04ca756fe484c694873968c5ca53748992b1e01..0e6a7ba716ce5ccbb2d28baf9e994cb5335fb93e 100644
--- a/debian/ai-auth-server.conf
+++ b/debian/ai-auth-server.conf
@@ -32,3 +32,10 @@ LDAP_BIND_DN = 'cn=manager, o=Anarchy'
 
 with open('/etc/ldap.secret') as fd:
     LDAP_BIND_PW = fd.read().strip()
+
+# Port mapping for the dovecot service on backends.
+NGINX_AUTH_PORT_MAP = {
+    'pop3': 10110,
+    'imap': 10143
+}
+