diff -Naur dovecot-2.2.21.orig/src/auth/auth-penalty.h dovecot-2.2.21/src/auth/auth-penalty.h
--- dovecot-2.2.21.orig/src/auth/auth-penalty.h	2015-12-09 16:39:10.000000000 +0100
+++ dovecot-2.2.21/src/auth/auth-penalty.h	2016-02-16 16:00:46.220188041 +0100
@@ -4,11 +4,11 @@
 struct auth_request;
 
 #define AUTH_PENALTY_INIT_SECS 2
-#define AUTH_PENALTY_MAX_SECS 15
+#define AUTH_PENALTY_MAX_SECS 60
 /* timeout specifies how long it takes for penalty to be irrelevant. */
 #define AUTH_PENALTY_TIMEOUT \
-	(AUTH_PENALTY_INIT_SECS + 4 + 8 + AUTH_PENALTY_MAX_SECS)
-#define AUTH_PENALTY_MAX_PENALTY 4
+	600
+#define AUTH_PENALTY_MAX_PENALTY 30
 
 /* If lookup failed, penalty and last_update are both zero */
 typedef void auth_penalty_callback_t(unsigned int penalty,