Email has made mass mailings possible at the touch of a button.

【mass】有了电子邮件，点击一个按钮就可以群发邮件。

The word " greetings" sounds like the opening of a form letter, or a mass mailing, so you should not use it in a letter to just one person.

单词" greetings" 听起来像是封格式信件或者是群发邮件的开头，因此不要在给单个人的信件中这样使用。