diff --git a/tests/multiple_domains_test.go b/tests/multiple_domains_test.go
new file mode 100644
index 00000000..971ca91b
--- /dev/null
+++ b/tests/multiple_domains_test.go
@@ -0,0 +1,271 @@
+//go:build integration
+
+/*
+Maddy Mail Server - Composable all-in-one email server.
+Copyright © 2019-2025 Max Mazurov <fox.cpp@disroot.org>, Maddy Mail Server contributors
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+package tests_test
+
+import (
+	"testing"
+
+	"github.com/foxcpp/maddy/tests"
+)
+
+// Test cases based on https://maddy.email/multiple-domains/
+
+func TestMultipleDomains_SeparateNamespace(tt *testing.T) {
+	tt.Parallel()
+	t := tests.NewT(tt)
+	t.DNS(nil)
+	t.Port("submission")
+	t.Port("imap")
+	t.Config(`
+		tls off
+		hostname test.maddy.email
+
+		auth.pass_table local_authdb {
+			table sql_table {
+				driver sqlite3
+				dsn credentials.db
+				table_name passwords
+			}
+		}
+		storage.imapsql local_mailboxes {
+			driver sqlite3
+			dsn imapsql.db
+		}
+
+		submission tcp://0.0.0.0:{env:TEST_PORT_submission} {
+			auth &local_authdb
+			reject
+		}
+		imap tcp://127.0.0.1:{env:TEST_PORT_imap} {
+			auth &local_authdb
+			storage &local_mailboxes
+		}
+	`)
+
+	t.MustRunCLIGroup(
+		[]string{"creds", "create", "-p", "user1", "user1@test1.maddy.email"},
+		[]string{"creds", "create", "-p", "user2", "user2@test1.maddy.email"},
+		[]string{"creds", "create", "-p", "user3", "user1@test2.maddy.email"},
+		[]string{"imap-acct", "create", "--no-specialuse", "user1@test1.maddy.email"},
+		[]string{"imap-acct", "create", "--no-specialuse", "user2@test1.maddy.email"},
+		[]string{"imap-acct", "create", "--no-specialuse", "user1@test2.maddy.email"},
+	)
+	t.Run(2)
+
+	user1 := t.Conn("imap")
+	user1.ExpectPattern(`\* OK *`)
+	user1.Writeln(`. LOGIN user1@test1.maddy.email user1`)
+	user1.ExpectPattern(`. OK *`)
+	user1.Writeln(`. CREATE user1`)
+	user1.ExpectPattern(`. OK *`)
+
+	user2 := t.Conn("imap")
+	user2.ExpectPattern(`\* OK *`)
+	user2.Writeln(`. LOGIN user2@test1.maddy.email user2`)
+	user2.ExpectPattern(`. OK *`)
+	user2.Writeln(`. CREATE user2`)
+	user2.ExpectPattern(`. OK *`)
+
+	user3 := t.Conn("imap")
+	user3.ExpectPattern(`\* OK *`)
+	user3.Writeln(`. LOGIN user1@test2.maddy.email user3`)
+	user3.ExpectPattern(`. OK *`)
+	user3.Writeln(`. CREATE user3`)
+	user3.ExpectPattern(`. OK *`)
+
+	user1.Writeln(`. LIST "" "*"`)
+	user1.Expect(`* LIST (\HasNoChildren) "." INBOX`)
+	user1.Expect(`* LIST (\HasNoChildren) "." "user1"`)
+	user1.ExpectPattern(". OK *")
+
+	user2.Writeln(`. LIST "" "*"`)
+	user2.Expect(`* LIST (\HasNoChildren) "." INBOX`)
+	user2.Expect(`* LIST (\HasNoChildren) "." "user2"`)
+	user2.ExpectPattern(". OK *")
+
+	user3.Writeln(`. LIST "" "*"`)
+	user3.Expect(`* LIST (\HasNoChildren) "." INBOX`)
+	user3.Expect(`* LIST (\HasNoChildren) "." "user3"`)
+	user3.ExpectPattern(". OK *")
+}
+
+func TestMultipleDomains_SharedCredentials_DistinctMailboxes(tt *testing.T) {
+	tt.Parallel()
+	t := tests.NewT(tt)
+	t.DNS(nil)
+	t.Port("submission")
+	t.Port("imap")
+	t.Config(`
+		tls off
+		hostname test.maddy.email
+		auth_map email_localpart
+
+		auth.pass_table local_authdb {
+			table sql_table {
+				driver sqlite3
+				dsn credentials.db
+				table_name passwords
+			}
+		}
+		storage.imapsql local_mailboxes {
+			driver sqlite3
+			dsn imapsql.db
+		}
+
+		submission tcp://0.0.0.0:{env:TEST_PORT_submission} {
+			auth &local_authdb
+			reject
+		}
+		imap tcp://127.0.0.1:{env:TEST_PORT_imap} {
+			auth &local_authdb
+			storage &local_mailboxes
+		}
+	`)
+
+	t.MustRunCLIGroup(
+		[]string{"creds", "create", "-p", "user1", "user1"},
+		[]string{"creds", "create", "-p", "user2", "user2"},
+		[]string{"imap-acct", "create", "--no-specialuse", "user1@test1.maddy.email"},
+		[]string{"imap-acct", "create", "--no-specialuse", "user2@test1.maddy.email"},
+		[]string{"imap-acct", "create", "--no-specialuse", "user1@test2.maddy.email"},
+	)
+	t.Run(2)
+
+	user1 := t.Conn("imap")
+	user1.ExpectPattern(`\* OK *`)
+	user1.Writeln(`. LOGIN user1@test1.maddy.email user1`)
+	user1.ExpectPattern(`. OK *`)
+	user1.Writeln(`. CREATE user1`)
+	user1.ExpectPattern(`. OK *`)
+
+	user2 := t.Conn("imap")
+	user2.ExpectPattern(`\* OK *`)
+	user2.Writeln(`. LOGIN user2@test1.maddy.email user2`)
+	user2.ExpectPattern(`. OK *`)
+	user2.Writeln(`. CREATE user2`)
+	user2.ExpectPattern(`. OK *`)
+
+	user3 := t.Conn("imap")
+	user3.ExpectPattern(`\* OK *`)
+	user3.Writeln(`. LOGIN user1@test2.maddy.email user1`)
+	user3.ExpectPattern(`. OK *`)
+	user3.Writeln(`. CREATE user3`)
+	user3.ExpectPattern(`. OK *`)
+
+	user1.Writeln(`. LIST "" "*"`)
+	user1.Expect(`* LIST (\HasNoChildren) "." INBOX`)
+	user1.Expect(`* LIST (\HasNoChildren) "." "user1"`)
+	user1.ExpectPattern(". OK *")
+
+	user2.Writeln(`. LIST "" "*"`)
+	user2.Expect(`* LIST (\HasNoChildren) "." INBOX`)
+	user2.Expect(`* LIST (\HasNoChildren) "." "user2"`)
+	user2.ExpectPattern(". OK *")
+
+	user3.Writeln(`. LIST "" "*"`)
+	user3.Expect(`* LIST (\HasNoChildren) "." INBOX`)
+	user3.Expect(`* LIST (\HasNoChildren) "." "user3"`)
+	user3.ExpectPattern(". OK *")
+}
+
+func TestMultipleDomains_SharedCredentials_SharedMailboxes(tt *testing.T) {
+	tt.Parallel()
+	t := tests.NewT(tt)
+	t.DNS(nil)
+	t.Port("submission")
+	t.Port("imap")
+	t.Config(`
+		tls off
+		hostname test.maddy.email
+		auth_map email_localpart_optional
+
+		auth.pass_table local_authdb {
+			table sql_table {
+				driver sqlite3
+				dsn credentials.db
+				table_name passwords
+			}
+		}
+		storage.imapsql local_mailboxes {
+			driver sqlite3
+			dsn imapsql.db
+
+			delivery_map email_localpart_optional
+		}
+
+		submission tcp://0.0.0.0:{env:TEST_PORT_submission} {
+			auth &local_authdb
+			reject
+		}
+		imap tcp://127.0.0.1:{env:TEST_PORT_imap} {
+			auth &local_authdb
+			storage &local_mailboxes
+
+			storage_map email_localpart_optional
+		}
+	`)
+
+	t.MustRunCLIGroup(
+		[]string{"creds", "create", "-p", "user1", "user1"},
+		[]string{"creds", "create", "-p", "user2", "user2"},
+		[]string{"imap-acct", "create", "--no-specialuse", "user1"},
+		[]string{"imap-acct", "create", "--no-specialuse", "user2"},
+	)
+	t.Run(2)
+
+	user1 := t.Conn("imap")
+	user1.ExpectPattern(`\* OK *`)
+	user1.Writeln(`. LOGIN user1 user1`)
+	user1.ExpectPattern(`. OK *`)
+	user1.Writeln(`. CREATE user1`)
+	user1.ExpectPattern(`. OK *`)
+
+	user2 := t.Conn("imap")
+	user2.ExpectPattern(`\* OK *`)
+	user2.Writeln(`. LOGIN user2@test1.maddy.email user2`)
+	user2.ExpectPattern(`. OK *`)
+	user2.Writeln(`. CREATE user2`)
+	user2.ExpectPattern(`. OK *`)
+
+	user12 := t.Conn("imap")
+	user12.ExpectPattern(`\* OK *`)
+	user12.Writeln(`. LOGIN user1@test2.maddy.email user1`)
+	user12.ExpectPattern(`. OK *`)
+	user12.Writeln(`. CREATE user12`)
+	user12.ExpectPattern(`. OK *`)
+
+	user1.Writeln(`. LIST "" "*"`)
+	user1.Expect(`* LIST (\HasNoChildren) "." INBOX`)
+	user1.Expect(`* LIST (\HasNoChildren) "." "user1"`)
+	user1.Expect(`* LIST (\HasNoChildren) "." "user12"`)
+	user1.ExpectPattern(". OK *")
+
+	user2.Writeln(`. LIST "" "*"`)
+	user2.Expect(`* LIST (\HasNoChildren) "." INBOX`)
+	user2.Expect(`* LIST (\HasNoChildren) "." "user2"`)
+	user2.ExpectPattern(". OK *")
+
+	user12.Writeln(`. LIST "" "*"`)
+	user12.Expect(`* LIST (\HasNoChildren) "." INBOX`)
+	user12.Expect(`* LIST (\HasNoChildren) "." "user1"`)
+	user12.Expect(`* LIST (\HasNoChildren) "." "user12"`)
+	user12.ExpectPattern(". OK *")
+}