diff --git a/helmfile/apps/open-xchange/values-openxchange.yaml.gotmpl b/helmfile/apps/open-xchange/values-openxchange.yaml.gotmpl
index e7f2cd88..0c04d970 100644
--- a/helmfile/apps/open-xchange/values-openxchange.yaml.gotmpl
+++ b/helmfile/apps/open-xchange/values-openxchange.yaml.gotmpl
@@ -237,12 +237,25 @@ appsuite:
       com.openexchange.authentication.oauth.clientSecret: {{ .Values.secrets.keycloak.clientSecret.as8oidc | quote }}
       # MAIL
       com.openexchange.mail.authType: "xoauth2"
-      com.openexchange.mail.loginSource: "mail"
+      com.openexchange.mail.loginSource: "name"
       com.openexchange.mail.mailServer: "dovecot"
       com.openexchange.mail.mailServerSource: "global"
       com.openexchange.mail.transport.authType: "xoauth2"
       com.openexchange.mail.transportServer: "postfix-ox"
       com.openexchange.mail.transportServerSource: "global"
+      # Mail Login Resolver
+      com.openexchange.mail.login.resolver.enabled: "true"
+      com.openexchange.mail.login.resolver.ldap.enabled: "true"
+      com.openexchange.mail.login.resolver.ldap.clientId: contactsLdapClient
+      com.openexchange.mail.login.resolver.ldap.mailLoginSearchFilter: "(&(univentionObjectType=users/user)(isOxUser=OK)(mailPrimaryAddress=[mailLogin]))"
+      com.openexchange.mail.login.resolver.ldap.userNameAttribute: uid
+      com.openexchange.mail.login.resolver.ldap.contextIdAttribute: oxContextIDNum
+      com.openexchange.mail.login.resolver.ldap.entitySearchFilter: "(&(univentionObjectType=users/user)(isOxUser=OK)(oxContextIDNum=[cid])(uid=[uname]))"
+      #com.openexchange.mail.login.resolver.ldap.mailLoginAttribute: entryUUID
+      # Workaround until either OX issue /appsuite/platform/core#251 is fixed
+      # or entryUUIDs are replaced by a different field.
+      com.openexchange.mail.login.resolver.ldap.mailLoginAttribute: departmentName
+      #com.openexchange.mail.login.resolver.ldap.cacheExpire: "1"
       # Requirements for OX-Connector
       com.openexchange.user.enforceUniqueDisplayName: "false"
       com.openexchange.folderstorage.database.preferDisplayName: "false"