diff --git a/go.sum b/go.sum
index a34ef8a..6ea1bea 100644
--- a/go.sum
+++ b/go.sum
@@ -174,6 +174,7 @@ golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGm
 golang.org/x/tools v0.0.0-20190606124116-d0a3d012864b/go.mod h1:/rFqwRUd4F7ZHNgwSSTFct+R/Kf4OFW1sUzUTQQTgfc=
 golang.org/x/tools v0.0.0-20190907020128-2ca718005c18 h1:xFbv3LvlvQAmbNJFCBKRv1Ccvnh9FVsW0FX2kTWWowE=
 golang.org/x/tools v0.0.0-20190907020128-2ca718005c18/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/tools v0.0.0-20191216052735-49a3e744a425 h1:VvQyQJN0tSuecqgcIxMWnnfG5kSmgy9KZR9sW3W5QeA=
 golang.org/x/tools v0.0.0-20191216052735-49a3e744a425/go.mod h1:TB2adYChydJhpapKDTa4BR/hXlZSLoq2Wpct/0txZ28=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
diff --git a/internal/check/milter/milter.go b/internal/check/milter/milter.go
index 5ca80ed..8cc1dec 100644
--- a/internal/check/milter/milter.go
+++ b/internal/check/milter/milter.go
@@ -85,7 +85,6 @@ type state struct {
 	session    *milter.ClientSession
 	msgMeta    *module.MsgMetadata
 	skipChecks bool
-	discarded  bool
 	log        log.Logger
 }
 
@@ -309,7 +308,9 @@ func (s *state) CheckSender(ctx context.Context, mailFrom string) module.CheckRe
 	if s.msgMeta.Conn.AuthUser != "" {
 		fields = append(fields, "auth_authen", s.msgMeta.Conn.AuthUser)
 	}
-	s.session.Macros(milter.CodeMail, fields...)
+	if err := s.session.Macros(milter.CodeMail, fields...); err != nil {
+		return s.ioError(err)
+	}
 
 	esmtpArgs := make([]string, 0, 2)
 	if s.msgMeta.SMTPOpts.UTF8 {