To ensure that the computer binds as expected when binding with System Preferences, Directory Utility, or dsconfigad, use computer names that:

• are less than 16 characters in length
• only contain alphanumeric (A–Z, a–z), numbers (0–9), - (dash) and/or _ (underscore) characters

Although the underscore character is valid in hostnames, it is not a valid component in a DNS domain name. If the Active Directory domain being bound to contains an underscore in the domain name, binding and services will not function as expected.

For more information about the length and character set requirements for use with Active Directory, see this Microsoft article.