ARCHIVED: If my computer has an underscore ( _ ) in its name, why am I having trouble accessing network services?

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The underscore is not a legal character for use in hostnames. As defined in RFC 822, the only legal characters are the following:

Alphanumeric (a-z and 0-9): Both uppercase and lowercase letters are acceptable, and the hostname is case insensitive. In other words, dvader.empire.gov is identical to DVADER.EMPIRE.GOV and Dvader.Empire.Gov.
Hyphen (-): Neither the first nor the last character in a hostname field should be a hyphen.
Period (.): The period should be used only to delimit fields in a hostname (e.g., dvader . empire . gov) .

If your computer has an underscore in its name (e.g., admiral_ozzel.empire.gov), you will have difficulty accessing services on TCP/IP networks. You may be unable to send email to certain hosts or to read Usenet newsgroups. The only way you'll be able to resolve these problems is to change your computer's name.