diff --git a/notify/email/email.go b/notify/email/email.go
index 73fcf577..33225403 100644
--- a/notify/email/email.go
+++ b/notify/email/email.go
@@ -18,6 +18,7 @@ import (
 	"context"
 	"crypto/tls"
 	"fmt"
+	"math/rand"
 	"mime"
 	"mime/multipart"
 	"mime/quotedprintable"
@@ -25,6 +26,7 @@ import (
 	"net/mail"
 	"net/smtp"
 	"net/textproto"
+	"os"
 	"strings"
 	"time"
 
@@ -41,9 +43,10 @@ import (
 
 // Email implements a Notifier for email notifications.
 type Email struct {
-	conf   *config.EmailConfig
-	tmpl   *template.Template
-	logger log.Logger
+	conf     *config.EmailConfig
+	tmpl     *template.Template
+	logger   log.Logger
+	hostname string
 }
 
 // New returns a new Email notifier.
@@ -57,7 +60,13 @@ func New(c *config.EmailConfig, t *template.Template, l log.Logger) *Email {
 	if _, ok := c.Headers["From"]; !ok {
 		c.Headers["From"] = c.From
 	}
-	return &Email{conf: c, tmpl: t, logger: l}
+
+	h, err := os.Hostname()
+	// If we can't get the hostname, we'll use localhost
+	if err != nil {
+		h = "localhost.localdomain"
+	}
+	return &Email{conf: c, tmpl: t, logger: l, hostname: h}
 }
 
 // auth resolves a string of authentication mechanisms.
@@ -236,6 +245,10 @@ func (n *Email) Notify(ctx context.Context, as ...*types.Alert) (bool, error) {
 		fmt.Fprintf(buffer, "%s: %s\r\n", header, mime.QEncoding.Encode("utf-8", value))
 	}
 
+	if _, ok := n.conf.Headers["Message-Id"]; !ok {
+		fmt.Fprintf(buffer, "Message-Id: %s\r\n", fmt.Sprintf("<%d.%d@%s>", time.Now().UnixNano(), rand.Uint64(), n.hostname))
+	}
+
 	multipartBuffer := &bytes.Buffer{}
 	multipartWriter := multipart.NewWriter(multipartBuffer)
 
diff --git a/notify/email/email_test.go b/notify/email/email_test.go
index 595d9912..0d1720b9 100644
--- a/notify/email/email_test.go
+++ b/notify/email/email_test.go
@@ -356,7 +356,7 @@ func TestEmailNotifyWithoutAuthentication(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	_, _, err = notifyEmail(
+	mail, _, err := notifyEmail(
 		&config.EmailConfig{
 			Smarthost: c.Smarthost,
 			To:        emailTo,
@@ -367,6 +367,18 @@ func TestEmailNotifyWithoutAuthentication(t *testing.T) {
 		c.Server,
 	)
 	require.NoError(t, err)
+	var (
+		foundMsgID bool
+		headers    []string
+	)
+	for k := range mail.Headers {
+		if strings.ToLower(k) == "message-id" {
+			foundMsgID = true
+			break
+		}
+		headers = append(headers, k)
+	}
+	require.True(t, foundMsgID, "Couldn't find 'message-id' in %v", headers)
 }
 
 // TestEmailNotifyWithSTARTTLS connects to the server, upgrades the connection