信笺

例句：

1. 1. She wrote a letter to her friend last week.
   她上周给朋友写了一封信。
2. 2. He sent a message to his boss via email.
   他通过电子邮件给老板发了信息。
3. 3. The postman delivered the mail to the doorstep.
   邮差把邮件送到门口。