diff --git a/mail/mailer.go b/mail/mailer.go
index 864cdbd51..21b2417f4 100644
--- a/mail/mailer.go
+++ b/mail/mailer.go
@@ -21,10 +21,14 @@ import (
 	"time"
 
 	"github.com/jmhodges/clock"
+	"golang.org/x/net/context"
 	"github.com/prometheus/client_golang/prometheus"
 
 	"github.com/letsencrypt/boulder/core"
+	"github.com/letsencrypt/boulder/bdns"
 	blog "github.com/letsencrypt/boulder/log"
+	berrors "github.com/letsencrypt/boulder/errors"
+	"github.com/letsencrypt/boulder/probs"
 )
 
 type idGenerator interface {
@@ -122,6 +126,7 @@ func New(
 	username,
 	password string,
 	rootCAs *x509.CertPool,
+	resolver bdns.Client,
 	from mail.Address,
 	logger blog.Logger,
 	stats prometheus.Registerer,
@@ -141,6 +146,7 @@ func New(
 			server:   server,
 			port:     port,
 			rootCAs:  rootCAs,
+			dnsClient: resolver,
 		},
 		log:              logger,
 		from:             from,
@@ -181,7 +187,7 @@ func (m *MailerImpl) generateMessage(to []string, subject, body string) ([]byte,
 		fmt.Sprintf("To: %s", strings.Join(addrs, ", ")),
 		fmt.Sprintf("From: %s", m.from.String()),
 		fmt.Sprintf("Subject: %s", subject),
-		fmt.Sprintf("Date: %s", now.Format(time.RFC822)),
+		fmt.Sprintf("Date: %s", now.Format(time.RFC1123Z)),
 		fmt.Sprintf("Message-Id: <%s.%s.%s>", now.Format("20060102T150405"), mid.String(), m.from.Address),
 		"MIME-Version: 1.0",
 		"Content-Type: text/plain; charset=UTF-8",
@@ -238,23 +244,32 @@ func (m *MailerImpl) Connect() error {
 type dialerImpl struct {
 	username, password, server, port string
 	rootCAs                          *x509.CertPool
+	dnsClient                        bdns.Client
 }
 
 func (di *dialerImpl) Dial() (smtpClient, error) {
-	hostport := net.JoinHostPort(di.server, di.port)
-	var conn net.Conn
-	var err error
-	conn, err = tls.Dial("tcp", hostport, &tls.Config{
-		RootCAs: di.rootCAs,
-	})
+	deadline := time.Now().Add(30 * time.Second)
+	ctx, cancel := context.WithDeadline(context.Background(), deadline)
+	defer cancel()
+
+	addrs, err := di.dnsClient.LookupHost(ctx, di.server)
 	if err != nil {
-		return nil, err
+		problem := probs.DNS("%v")
+		return nil, problem
 	}
-	client, err := smtp.NewClient(conn, di.server)
+	if len(addrs) == 0 {
+		return nil, berrors.DNSError("No valid IP addresses found for %s", di.server)
+	}
+
+	hostport := net.JoinHostPort(addrs[0].String(), di.port)
+	client, err := smtp.Dial(hostport)
 	if err != nil {
 		return nil, err
 	}
-	auth := smtp.PlainAuth("", di.username, di.password, di.server)
+	client.StartTLS( &tls.Config{
+		ServerName: di.server,
+	})
+	auth := smtp.PlainAuth("", di.username, di.password, addrs[0].String())
 	if err = client.Auth(auth); err != nil {
 		return nil, err
 	}