diff --git a/crates/directory/src/backend/ldap/lookup.rs b/crates/directory/src/backend/ldap/lookup.rs
index e1dd9fc4..b6fae9dc 100644
--- a/crates/directory/src/backend/ldap/lookup.rs
+++ b/crates/directory/src/backend/ldap/lookup.rs
@@ -366,11 +366,11 @@ impl LdapMappings {
                 }
             } else if self.attr_email_address.contains(&attr) {
                 for item in value {
-                    principal.prepend_str(PrincipalField::Emails, item);
+                    principal.prepend_str(PrincipalField::Emails, item.to_lowercase());
                 }
             } else if self.attr_email_alias.contains(&attr) {
                 for item in value {
-                    principal.append_str(PrincipalField::Emails, item);
+                    principal.append_str(PrincipalField::Emails, item.to_lowercase());
                 }
             } else if let Some(idx) = self.attr_description.iter().position(|a| a == &attr) {
                 if !principal.has_field(PrincipalField::Description) || idx == 0 {
diff --git a/crates/directory/src/backend/sql/lookup.rs b/crates/directory/src/backend/sql/lookup.rs
index 141ed497..8fdbc4be 100644
--- a/crates/directory/src/backend/sql/lookup.rs
+++ b/crates/directory/src/backend/sql/lookup.rs
@@ -291,7 +291,7 @@ impl SqlMappings {
                     }
                 } else if name.eq_ignore_ascii_case(&self.column_email) {
                     if let Value::Text(text) = value {
-                        principal.set(PrincipalField::Emails, text.into_owned());
+                        principal.set(PrincipalField::Emails, text.to_lowercase());
                     }
                 } else if name.eq_ignore_ascii_case(&self.column_quota) {
                     if let Value::Integer(quota) = value {