When POP, IMAP and SMTP users authenticate, they typically provide an unqualified user ID (a user ID without a domain portion). The value of the
defaultdomain option is appended to unqualified user IDs. When used as an MMP virtual domain option, this allows a single MMP server with multiple IP addresses to support unqualified user IDs for multiple hosted domains. This may also be set as a service-wide option.
Use with base
defaultdomain base option specifies the Messaging Server default domain. This is used to determine whether a domain is the default domain or a hosted domain.
defaultdomain base option is set to an appropriate value during initial configuration.
The MTA has a "twin" option,
ldap_default_domain, that can override the
defaultdomain base option for MTA purposes. See the description of
ldap_default_domain for details on how the MTA uses the
defaultdomain value (if
ldap_default_domain is not set).