Signature lines will be a part of your messages. Keep in mind that by default the contents of your signature file are added to every email message that you send, including email that may be a part of formal communications and processes. Increasingly, email programs allow you to format your email, using colors, font sizes, images, bold underlines, etc. In general use simple text in your email messages. Minimize use of attachments.
Attachments also take time to handle, often unnecessarily.
In general cut and paste materials directly into your email messages and send them as text.