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.
This policy will probably inform you that email is to be used only for everyday business purposes, that the computer systems at work are the property of your employer, that email may be monitored, and that you have no reasonable expectation of privacy in your use of email.