Just about every email client program and online service such as Yahoo and Hotmail offer the ability to attach files to an email. This mean you can add pictures, written documents and nearly every type of file. It is best not to attach a file which is too large though, because it may take just too long to send and receive the email. Attaching a file is usually very straight and easy to perform, when writing an email there will usually be an option at the bottom to add an attachment.