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.
A business letter is a formal letter with six parts: The Heading. The heading contains the return address with the date on the last line. Sometimes it is necessary to include a line before the date with a phone number, fax number, or e-mail address. Often there is a line skipped between the address and the date. It is not necessary to type a return address if you are using stationery with the return address already imprinted, but you should always use a date.