1、The email was sent with a signatureless reply, making it difficult to identify the sender.
这封电子邮件是没有签名的回复，很难确定发件人。
2、The document appeared to be unsigned and signatureless, raising suspicions about its authenticity.
这份文件看起来没有签名，没有任何签名标记，引发了对其真实性的怀疑。