diff --git a/go.mod b/go.mod
index c127cf09..eb3d60c0 100644
--- a/go.mod
+++ b/go.mod
@@ -17,7 +17,7 @@ require (
 	github.com/cenkalti/backoff v2.2.1+incompatible
 	github.com/d4l3k/messagediff v1.2.2-0.20190829033028-7e0a312ae40b
 	github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21
-	github.com/emersion/go-smtp v0.16.0
+	github.com/emersion/go-smtp v0.18.1
 	github.com/google/go-cmp v0.6.0
 	github.com/google/subcommands v1.2.0
 	github.com/google/uuid v1.4.0
diff --git a/go.sum b/go.sum
index faa1721f..5543f36a 100644
--- a/go.sum
+++ b/go.sum
@@ -344,8 +344,8 @@ github.com/dustin/go-humanize v1.0.1/go.mod h1:Mu1zIs6XwVuF/gI1OepvI0qD18qycQx+m
 github.com/elazarl/goproxy v0.0.0-20230731152917-f99041a5c027 h1:1L0aalTpPz7YlMxETKpmQoWMBkeiuorElZIXoNmgiPE=
 github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21 h1:OJyUGMJTzHTd1XQp98QTaHernxMYzRaOasRir9hUlFQ=
 github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21/go.mod h1:iL2twTeMvZnrg54ZoPDNfJaJaqy0xIQFuBdrLsmspwQ=
-github.com/emersion/go-smtp v0.16.0 h1:eB9CY9527WdEZSs5sWisTmilDX7gG+Q/2IdRcmubpa8=
-github.com/emersion/go-smtp v0.16.0/go.mod h1:qm27SGYgoIPRot6ubfQ/GpiPy/g3PaZAVRxiO/sDUgQ=
+github.com/emersion/go-smtp v0.18.1 h1:4DFV0jxKhq0Gqt/Br3BRHyKZy5TStk6NIMHAx6GE/LA=
+github.com/emersion/go-smtp v0.18.1/go.mod h1:qm27SGYgoIPRot6ubfQ/GpiPy/g3PaZAVRxiO/sDUgQ=
 github.com/emicklei/go-restful/v3 v3.8.0 h1:eCZ8ulSerjdAiaNpF7GxXIE7ZCMo1moN1qX+S609eVw=
 github.com/emirpasic/gods v1.18.1 h1:FXtiHYKDGKCW2KzwZKx0iC0PQmdlorYgdFG9jPXJ1Bc=
 github.com/envoyproxy/go-control-plane v0.9.0/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
diff --git a/reporter/email.go b/reporter/email.go
index c149785e..4f9f4fdc 100644
--- a/reporter/email.go
+++ b/reporter/email.go
@@ -133,7 +133,7 @@ func (e *emailSender) sendMail(smtpServerAddr, message string) (err error) {
 		return xerrors.Errorf("Failed to send Mail command: %w", err)
 	}
 	for _, to := range emailConf.To {
-		if err = c.Rcpt(to); err != nil {
+		if err = c.Rcpt(to, nil); err != nil {
 			return xerrors.Errorf("Failed to send Rcpt command: %w", err)
 		}
 	}