diff --git a/apps/kolab_guam/src/kolab_guam_session.erl b/apps/kolab_guam/src/kolab_guam_session.erl
--- a/apps/kolab_guam/src/kolab_guam_session.erl
+++ b/apps/kolab_guam/src/kolab_guam_session.erl
@@ -255,13 +255,15 @@
     apply_next_rule_serverside(ImapSession, ServerData, [], CurrentlyActiveRules).
 
 apply_next_rule_serverside(_ImapSession, ServerData, ActiveRulesAcc, []) -> { ServerData, lists:reverse(ActiveRulesAcc) };
+apply_next_rule_serverside(_ImapSession, ServerData, [], undefined) ->
+    { ServerData, [] };
 apply_next_rule_serverside(ImapSession, ServerData, ActiveRulesAcc, [{ Module, RuleState } | ActiveRules]) ->
     %TODO: allow rules to remove themselves from the action during serverside processing?
     { ModifiedData, ModifiedRuleState } = Module:apply_to_server_message(ImapSession, ServerData, RuleState),
     apply_next_rule_serverside(ImapSession, ModifiedData, [{ Module, ModifiedRuleState } | ActiveRulesAcc], ActiveRules).
 
 apply_ruleset_clientside(_ImapSession, _Socket, ClientData, _CurrentCommandSplit, [], []) ->
-    { ClientData, [], [], perform_passthrough, undefined };
+    { ClientData, [], [], undefined, undefined, perform_passthrough };
 apply_ruleset_clientside(ImapSession, Socket, ClientData, CurrentCommandSplit, UndecidedRules, CurrentlyActiveRules) ->
     { PostAction, SplitCommand, SplitResetTrigger } =
         case CurrentCommandSplit of
@@ -287,6 +289,7 @@
     { Rules, [] };
 check_undecided(Socket, ClientData, SplitCommand, Rules) -> check_next_undecided_rule(Socket, ClientData, SplitCommand, Rules, { [], [] }).
 check_next_undecided_rule(_Socket, _ClientData, _SplitCommand, [], Accs) -> Accs;
+check_next_undecided_rule(_Socket, _ClientData, _SplitCommand, undefined, Accs) -> Accs;
 check_next_undecided_rule(Socket, ClientData, SplitCommand, [Rule|Rules], { UndecidedAcc, NewActiveAcc }) ->
     { Module, RuleState } = Rule,
     %%lager:debug("Does ~p apply with state ~p? let's find out!", [Module, RuleState]),