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.
So before you send the next batch of letters, find out the main differences between First Class, Priority, and Certified mail. First Class Mail. If you're sending a letter or small package that weighs 13 ounces or less, First Class mail is the least expensive option. For this reason, many businesses opt for this service, whether they're sending bills, invoices, personal letters, cards or small parcels. This type of mail usually arrives within one to three days. Priority Mail