diff --git a/email.go b/email.go
index 64af7b5..15e419e 100644
--- a/email.go
+++ b/email.go
@@ -9,6 +9,7 @@ import (
 	"net/mail"
 	"net/textproto"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/toorop/go-dkim"
@@ -786,6 +787,13 @@ func (server *SMTPServer) Connect() (*SMTPClient, error) {
 		tlsConfig = &tls.Config{ServerName: server.Host}
 	}
 
+	if server.Helo == "" {
+		atIndex := strings.LastIndex(server.Username, "@")
+		if atIndex >= 0 {
+			server.Helo = server.Username[atIndex+1:]
+		}
+	}
+
 	// if there is a ConnectTimeout, setup the channel and do the connect under a goroutine
 	if server.ConnectTimeout != 0 {
 		smtpConnectChannel = make(chan error, 2)