diff --git a/protonmail/messages.go b/protonmail/messages.go
index 00738ea..e5571d1 100644
--- a/protonmail/messages.go
+++ b/protonmail/messages.go
@@ -331,18 +331,17 @@ func (set *MessagePackageSet) AddCleartext(addr string) error {
 }
 
 func serializeEncryptedKey(symKey *packet.EncryptedKey, pub *packet.PublicKey, config *packet.Config) (string, error) {
-	var armored bytes.Buffer
-	ciphertext, err := armor.Encode(&armored, "PGP MESSAGE", nil)
+	var encoded bytes.Buffer
+	ciphertext := base64.NewEncoder(base64.StdEncoding, &encoded)
+
+	err := packet.SerializeEncryptedKey(ciphertext, pub, symKey.CipherFunc, symKey.Key, config)
 	if err != nil {
 		return "", err
 	}
 
-	err = packet.SerializeEncryptedKey(ciphertext, pub, symKey.CipherFunc, symKey.Key, config)
-	if err != nil {
-		return "", err
-	}
+	ciphertext.Close()
 
-	return armored.String(), nil
+	return encoded.String(), nil
 }
 
 func (set *MessagePackageSet) AddInternal(addr string, pub *openpgp.Entity) error {
diff --git a/smtp/smtp.go b/smtp/smtp.go
index 61d6bf8..cb88e3c 100644
--- a/smtp/smtp.go
+++ b/smtp/smtp.go
@@ -210,7 +210,27 @@ func (u *user) Send(from string, to []string, r io.Reader) error {
 	}
 
 	if len(encryptedRecipients) > 0 {
-		// TODO
+		encryptedSet := protonmail.NewMessagePackageSet(nil)
+
+		plaintext, err := encryptedSet.Encrypt(bodyType)
+		if err != nil {
+			return err
+		}
+		if _, err := io.Copy(plaintext, bytes.NewReader(body.Bytes())); err != nil {
+			plaintext.Close()
+			return err
+		}
+		if err := plaintext.Close(); err != nil {
+			return err
+		}
+
+		for rcpt, pub := range encryptedRecipients {
+			if err := encryptedSet.AddInternal(rcpt, pub); err != nil {
+				return err
+			}
+		}
+
+		outgoing.Packages = append(outgoing.Packages, encryptedSet)
 	}
 
 	_, _, err = u.c.SendMessage(outgoing)