I remember LDAP login being a bit tricky for Zimba GAL. Perhaps this may shed light on MailArchive (which I've no experience with).
Here's our search base example which contained 'administrator';
LDAP search base: ou=Users,ou=company,dc=domain,dc=ourdomain,dc=com'
We ended up tracking the user down through it's LDAP OU's like this 'Bind DN: cn=administrator,cn=users,dc=domain,dc=ourdomain,d c=com'.
So, amorgan might be situated in LDAP like 'cn=amorgan,cn=users,dc=domain,dc=ourdomain,dc=com ' |