寄信

例句：

1. 1. I need to send this letter to my friend in Beijing.
   我需要把这封信寄给我在北京的朋友。
2. 2. Please make sure the package is properly sealed before sending it.
   请确保包裹在寄出前妥善封好。
3. 3. The post office is closed on Sundays, so we can't send the package until Monday.
   邮局周日不营业，所以我们周一才能寄出包裹。