Q. Does the InterMapper Authentication server support anonymous binds and LDAP search filters?
A. When IMAuth relays an authentication attempt to LDAP, it does so by first making an anonymous bind, just to query the list of supported authentication types. It then uses either simple or SASL DIGEST-MD5, depending on how you've configured it, and what's supported by your directory.
IMAuth does not yet support LDAP filters, beyond being able to specify a base DN and search field.
Currently, if we can't use an Anonymous bind LDAP authentication will fail.