When considering the cost of roofing materials, many people take into account just the shingle prices. This is incorrect, as a roof made just of roofing shingles will not work. You also need to consider all the accessories that are included in a complete roof system.
The differences between emails and letters is that, emails are send electronically and arrives faster to the person that you are sending it too, while in the other hand letters takes a little bit longer to arrives to the person and can be lost from the mailing company especially whens sending it overseas also it cost money.
Those naming and designing this email feature probably had the real world counterpart to email in mind: letters. 1  Carbon copy paper made it possible to send the same letter to two (or even more if you hit the keys really hard) different people without the onerous task of having to write or type it twice.