Always use attachments carefully. Recognize that the “size” of the e-mail depends upon how much you attach to it. A text-only e-mail is typically very small, only a few kilobytes. Adding one or more attachments can really increase the e-mail's size, especially if there are many graphics included in the attached file(s). A GIS (geographic information systems) map, for instance, may be quite large (several megabytes) because it is a graphics-based file. Be sure that the people who receive your e-mails can handle the size of any attachments you choose to send. Those on a dial-up modem, which remains the only option available in many locations, will experience slow service while a large file is being downloaded. In some cases, a large attachment may mean that the intended recipient does not receive your e-mail. In many instances, a better approach may be to post the document on your website somewhere and include the link to the document within the text of your e-mail message. That way, the recipient can decide if and when to retrieve the file. Be advised never to open attachments from unknown senders. These attachments may contain viruses or other damaging files.