diff --git a/pkg/server/smtp/handler.go b/pkg/server/smtp/handler.go
index f513a62..fcae44e 100644
--- a/pkg/server/smtp/handler.go
+++ b/pkg/server/smtp/handler.go
@@ -536,7 +536,7 @@ func (s *Session) parseArgs(arg string) (args map[string]string, ok bool) {
 	re := regexp.MustCompile(` (\w+)=(\w+)`)
 	pm := re.FindAllStringSubmatch(arg, -1)
 	if pm == nil {
-		s.logger.Warn().Msgf("Failed to parse arg string: %q")
+		s.logger.Warn().Msgf("Failed to parse arg string: %q", arg)
 		return nil, false
 	}
 	for _, m := range pm {