Sometimes in English, when we want to refer to postal mail, not email or anything online, we call it snail mail 'cause it takes such a long time to travel like a snail.

有时候我们会想用英语写信件，而不是电子邮件或任何其它在线内容，我们称它为“蜗牛邮件”，因为它像蜗牛一样要花很长时间。