Hi,
I tried tonight with trace logs.
Problem seems to be that with external directories, server first cache aliases from external directory and then when an email inbound, it look in cache entries if full recipient exists, no more obfuscating subaddress. So it can’t find user+test in cache and don’t ask to external directory.
2026-06-03T21:04:46Z INFO DSN permanent failure notification (delivery.dsn-perm-fail) queueId = 310883167003258880, queueName = “local”, from = “[email protected]”, to = [“[email protected]”], size = 4222, total = 1, to = “[email protected]”, hostname = “localhost”, details = “Unexpected response for RCPT TO:[email protected]: Code: 550, Enhanced code: 5.5.0, Message: Mailbox not found.”, total = 0
2026-06-03T21:04:46Z DEBUG Cache miss (store.cache-miss) key = “user+test”, domain = 1, collection = “email”
2026-06-03T21:04:46Z DEBUG Cache hit (store.cache-hit) key = 1, collection = “domainId”
2026-06-03T21:04:46Z DEBUG Cache hit (store.cache-hit) key = “mydomain.com”, collection = “domainName”
2026-06-03T21:04:46Z TRACE Blob read operation (store.blob-read) key = base64:3MiViBee0jKDvrql2Oo6ZpQzx62xEzDS2RbpgkoCaDQ=, elapsed = 0ms, size = 2651
2026-06-03T21:04:46Z INFO New delivery attempt for domain (delivery.domain-delivery-start) queueId = 310883167003258880, queueName = “local”, from = “[email protected]”, to = [“[email protected]”], size = 4222, total = 1, domain = “mydomain.com”