Hello Postfix + LDAP , Samba as LDAP server, Dovecot virtual_transport set in postfix to dovecot-lmtp ( for autoresponder support ) Users have their email aliases in the otherMailbox record For example, account_test@example-domain user has an alias: test@exmaple-domain Query from command line works fine: postmap -q test@example-domain ldap://etc/postfix/ad_virtual_ account_test/Maildir/ (The filter in the query ad_virtual_mailbox_maps2.cf looks like this: [cut] scope = sub query_filter = (&(objectclass=person)(|(mail= result_attribute= uid result_format = %u/Maildir/ ) However, sending an email to the alias test@example-domain ends: Feb 28 12:31:40 mbox-01 postfix/lmtp[13474]: 2367A6EF: to=<test@example-domain>, relay=mbox-01[private/dovecot- delay=0.05, delays=0.02/0/0.02, dsn=5.1.1, status=bounced (host mbox-01[private/dovecot-lmtp] said: 550 5.1.1 <test@example-domain> User doesn't exist: test@example-domain (in reply to RCPT TO command)) I modified dovecot-ldap.conf.ext: I changed: user_filter = (&(objectClass=person)(uid=%u) to: user_filter = (&(objectClass=person)(|(uid=% but that didn't solve the problem. Where's the bug?  Any hint? Below dovecot configuration: # 2.3.4.1 (f79e8e7e4): /etc/dovecot/dovecot.conf # Pigeonhole version 0.5.4 () # OS: Linux 4.19.0-6-amd64 x86_64 Debian 10.2 # Hostname: mbox-01 auth_cache_negative_ttl = 0 auth_username_format = %Ln disable_plaintext_auth = no mail_gid = vmail mail_location = mbox:~/mail:INBOX=/var/mailbox mail_privileged_group = mail mail_uid = vmail managesieve_notify_capability = mailto managesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date index ihave duplicate mime foreverypart extracttext vacation-seconds namespace inbox {   inbox = yes   location =   mailbox Drafts {     special_use = \Drafts   }   mailbox Junk {     special_use = \Junk   }   mailbox Sent {     special_use = \Sent   }   mailbox "Sent Messages" {     special_use = \Sent   }   mailbox Trash {     special_use = \Trash   }   prefix = } passdb {   args = /etc/dovecot/dovecot-ldap.conf   driver = ldap } plugin {   sieve = /var/mailbox-store/%u/.dovecot   sieve_dir = /var/mailbox-store/%u   sieve_extensions = +vacation-seconds   sieve_trace_debug = yes   sieve_trace_dir = /tmp/sieve/   sieve_trace_level = matching   sieve_vacation_default_period = 10d   sieve_vacation_max_period = 30d   sieve_vacation_min_period = 1h } protocols = " imap lmtp sieve pop3 sieve" service auth {   unix_listener /var/spool/postfix/private/aut {     group = postfix     mode = 0666     user = postfix   }   unix_listener auth-userdb {     mode = 0666     user = vmail   } } service lmtp {   unix_listener /var/spool/postfix/private/dov {     group = postfix     mode = 0600     user = postfix   } } service managesieve-login {   inet_listener sieve {     port = 4190   }   process_min_avail = 0   service_count = 1   vsz_limit = 64 M } service managesieve {   process_limit = 1024 } service stats {   unix_listener stats-reader {     group = vmail     mode = 0660     user = vmail   }   unix_listener stats-writer {     group = vmail     mode = 0660     user = vmail   } } ssl_cert = </etc/dovecot/private/dovecot. ssl_client_ca_dir = /etc/ssl/certs ssl_dh = # hidden, use -P to show it ssl_key = # hidden, use -P to show it userdb {   args = /etc/dovecot/dovecot-ldap.conf   driver = ldap } protocol lmtp {   mail_plugins = " sieve" } protocol lda {   info_log_path = /var/log/dovecot-lda.log   log_path = /var/log/dovecot-lda-errors.lo   mail_plugins = " sieve" } and  dovecot-ldap.conf.ext: [cut] deref = never scope = subtree user_attrs = =mail=maildir:/var/mailbox-sto user_filter = (&(objectClass=person)(|(uid=% pass_attrs = uid=user,userPassword=password pass_filter = (&(objectClass=person)(uid=%u) default_pass_scheme = CRYPT