diff --git a/dev/Sieve/Commands.js b/dev/Sieve/Commands.js
index 234a35a98..49a2dabfa 100644
--- a/dev/Sieve/Commands.js
+++ b/dev/Sieve/Commands.js
@@ -102,6 +102,10 @@ export class FileIntoCommand extends GrammarCommand
 
 	toString()
 	{
+		// https://datatracker.ietf.org/doc/html/rfc3894
+		// :copy
+		// https://datatracker.ietf.org/doc/html/rfc5490#section-3.2
+		// :create
 		return 'fileinto ' + this._mailbox + ';';
 	}
 
@@ -137,6 +141,8 @@ export class RedirectCommand extends GrammarCommand
 
 	toString()
 	{
+		// https://datatracker.ietf.org/doc/html/rfc3894
+		// :copy
 		return 'redirect ' + this._address + ';';
 	}
 
diff --git a/dev/Sieve/Extensions/rfc5173.js b/dev/Sieve/Extensions/rfc5173.js
index 2cbefab87..31b299053 100644
--- a/dev/Sieve/Extensions/rfc5173.js
+++ b/dev/Sieve/Extensions/rfc5173.js
@@ -8,7 +8,7 @@ import {
 	GrammarTest
 } from 'Sieve/Grammar';
 
-export class BodyCommand extends GrammarTest
+export class BodyTest extends GrammarTest
 {
 	constructor()
 	{
diff --git a/dev/Sieve/Extensions/rfc5183.js b/dev/Sieve/Extensions/rfc5183.js
index eeb57d2e1..943f17f01 100644
--- a/dev/Sieve/Extensions/rfc5183.js
+++ b/dev/Sieve/Extensions/rfc5183.js
@@ -8,7 +8,7 @@ import {
 	GrammarTest
 } from 'Sieve/Grammar';
 
-export class EnvironmentCommand extends GrammarTest
+export class EnvironmentTest extends GrammarTest
 {
 	constructor()
 	{
diff --git a/dev/Sieve/Extensions/rfc5229.js b/dev/Sieve/Extensions/rfc5229.js
index d29bd1707..9076125d6 100644
--- a/dev/Sieve/Extensions/rfc5229.js
+++ b/dev/Sieve/Extensions/rfc5229.js
@@ -45,7 +45,7 @@ export class SetCommand extends GrammarCommand
 	}
 }
 
-export class StringCommand extends GrammarTest
+export class StringTest extends GrammarTest
 {
 	constructor()
 	{
diff --git a/dev/Sieve/Extensions/rfc5232.js b/dev/Sieve/Extensions/rfc5232.js
index 2f9c319bf..3e5f378e3 100644
--- a/dev/Sieve/Extensions/rfc5232.js
+++ b/dev/Sieve/Extensions/rfc5232.js
@@ -63,7 +63,7 @@ export class RemoveFlagCommand extends FlagCommand
 {
 }
 
-export class HasFlagCommand extends GrammarTest
+export class HasFlagTest extends GrammarTest
 {
 	constructor()
 	{
diff --git a/dev/Sieve/Extensions/rfc5235.js b/dev/Sieve/Extensions/rfc5235.js
index 982da394c..0147159f7 100644
--- a/dev/Sieve/Extensions/rfc5235.js
+++ b/dev/Sieve/Extensions/rfc5235.js
@@ -8,7 +8,7 @@ import {
 	GrammarTest
 } from 'Sieve/Grammar';
 
-export class SpamTestCommand extends GrammarTest
+export class SpamTestTest extends GrammarTest
 {
 	constructor()
 	{
@@ -41,7 +41,7 @@ export class SpamTestCommand extends GrammarTest
 	}
 }
 
-export class VirusTestCommand extends GrammarTest
+export class VirusTestTest extends GrammarTest
 {
 	constructor()
 	{
diff --git a/dev/Sieve/Extensions/rfc5260.js b/dev/Sieve/Extensions/rfc5260.js
index 9911cb1c4..03d6b6d2b 100644
--- a/dev/Sieve/Extensions/rfc5260.js
+++ b/dev/Sieve/Extensions/rfc5260.js
@@ -9,7 +9,7 @@ import {
 	GrammarTest
 } from 'Sieve/Grammar';
 
-export class DateCommand extends GrammarTest
+export class DateTest extends GrammarTest
 {
 	constructor()
 	{
@@ -62,7 +62,7 @@ export class DateCommand extends GrammarTest
 	}
 }
 
-export class CurrentDateCommand extends GrammarTest
+export class CurrentDateTest extends GrammarTest
 {
 	constructor()
 	{
diff --git a/dev/Sieve/Extensions/rfc5490.js b/dev/Sieve/Extensions/rfc5490.js
new file mode 100644
index 000000000..aa9409de3
--- /dev/null
+++ b/dev/Sieve/Extensions/rfc5490.js
@@ -0,0 +1,151 @@
+/**
+ * https://tools.ietf.org/html/rfc5490
+ */
+
+import {
+	GrammarTest,
+	GrammarString,
+	GrammarStringList
+} from 'Sieve/Grammar';
+
+/**
+ * https://datatracker.ietf.org/doc/html/rfc5490#section-3.1
+ */
+export class MailboxExistsTest extends GrammarTest
+{
+	constructor()
+	{
+		super();
+		this.mailbox_names = new GrammarStringList;
+	}
+
+	get require() { return 'mailbox'; }
+
+	toString()
+	{
+		return 'mailboxexists ' + this.mailbox_names + ';';
+	}
+
+	pushArguments(args)
+	{
+		if (args[0] instanceof GrammarStringList) {
+			this.mailbox_names = args[0];
+		}
+	}
+}
+
+/**
+ * https://datatracker.ietf.org/doc/html/rfc5490#section-3.3
+ */
+export class MetadataTest extends GrammarTest
+{
+	constructor()
+	{
+		super();
+		this.mailbox = new GrammarString;
+		this.annotation_name = new GrammarString;
+		this.key_list = new GrammarStringList;
+	}
+
+	get require() { return 'mboxmetadata'; }
+
+	toString()
+	{
+		return 'metadata '
+			+ ' ' + this.match_type
+			+ (this.comparator ? ' :comparator ' + this.comparator : '')
+			+ ' ' + this.mailbox
+			+ ' ' + this.annotation_name
+			+ ' ' + this.key_list.toString();
+	}
+
+	pushArguments(args)
+	{
+		this.mailbox = args[args.length-3];
+		this.annotation_name = args[args.length-2];
+		this.key_list = args[args.length-1];
+	}
+}
+
+/**
+ * https://datatracker.ietf.org/doc/html/rfc5490#section-3.4
+ */
+export class MetadataExistsTest extends GrammarTest
+{
+	constructor()
+	{
+		super();
+		this.mailbox = new GrammarString;
+		this.annotation_names = new GrammarStringList;
+	}
+
+	get require() { return 'mboxmetadata'; }
+
+	toString()
+	{
+		return 'metadataexists '
+			+ ' ' + this.mailbox
+			+ ' ' + this.annotation_names;
+	}
+
+	pushArguments(args)
+	{
+		this.mailbox = args[args.length-2];
+		this.annotation_names = args[args.length-1];
+	}
+}
+
+/**
+ * https://datatracker.ietf.org/doc/html/rfc5490#section-3.3
+ */
+export class ServerMetadataTest extends GrammarTest
+{
+	constructor()
+	{
+		super();
+		this.annotation_name = new GrammarString;
+		this.key_list = new GrammarStringList;
+	}
+
+	get require() { return 'servermetadata'; }
+
+	toString()
+	{
+		return 'servermetadata '
+			+ ' ' + this.match_type
+			+ (this.comparator ? ' :comparator ' + this.comparator : '')
+			+ ' ' + this.annotation_name
+			+ ' ' + this.key_list.toString();
+	}
+
+	pushArguments(args)
+	{
+		this.annotation_name = args[args.length-2];
+		this.key_list = args[args.length-1];
+	}
+}
+
+/**
+ * https://datatracker.ietf.org/doc/html/rfc5490#section-3.4
+ */
+export class ServerMetadataExistsTest extends GrammarTest
+{
+	constructor()
+	{
+		super();
+		this.annotation_names = new GrammarStringList;
+	}
+
+	get require() { return 'servermetadata'; }
+
+	toString()
+	{
+		return 'servermetadataexists '
+			+ ' ' + this.annotation_names;
+	}
+
+	pushArguments(args)
+	{
+		this.annotation_names = args[args.length-1];
+	}
+}
diff --git a/dev/Sieve/Grammar.js b/dev/Sieve/Grammar.js
index 93381926c..b656b3ca8 100644
--- a/dev/Sieve/Grammar.js
+++ b/dev/Sieve/Grammar.js
@@ -231,7 +231,7 @@ export class GrammarTest
 {
 	constructor(identifier)
 	{
-		this.identifier = identifier || this.constructor.name.toLowerCase().replace('command', '');
+		this.identifier = identifier || this.constructor.name.toLowerCase().replace(/test$/, '');
 		// Almost every test has a comparator and match_type, so define them here
 		this.comparator = '',
 		this.match_type = ':is',
diff --git a/dev/Sieve/Parser.js b/dev/Sieve/Parser.js
index 729d00a01..92e705d25 100644
--- a/dev/Sieve/Parser.js
+++ b/dev/Sieve/Parser.js
@@ -39,32 +39,32 @@ import {
 } from 'Sieve/Commands';
 
 import {
-	AddressCommand,
-	AllOfCommand,
-	AnyOfCommand,
-	EnvelopeCommand,
-	ExistsCommand,
-	FalseCommand,
-	HeaderCommand,
-	NotCommand,
-	SizeCommand,
-	TrueCommand
+	AddressTest,
+	AllOfTest,
+	AnyOfTest,
+	EnvelopeTest,
+	ExistsTest,
+	FalseTest,
+	HeaderTest,
+	NotTest,
+	SizeTest,
+	TrueTest
 } from 'Sieve/Tests';
 
-import { BodyCommand } from 'Sieve/Extensions/rfc5173';
-import { EnvironmentCommand } from 'Sieve/Extensions/rfc5183';
-import { SetCommand, StringCommand } from 'Sieve/Extensions/rfc5229';
+import { BodyTest } from 'Sieve/Extensions/rfc5173';
+import { EnvironmentTest } from 'Sieve/Extensions/rfc5183';
+import { SetCommand, StringTest } from 'Sieve/Extensions/rfc5229';
 import { VacationCommand } from 'Sieve/Extensions/rfc5230';
 
 import {
 	SetFlagCommand,
 	AddFlagCommand,
 	RemoveFlagCommand,
-	HasFlagCommand
+	HasFlagTest
 } from 'Sieve/Extensions/rfc5232';
 
-import { SpamTestCommand, VirusTestCommand } from 'Sieve/Extensions/rfc5235';
-import { DateCommand, CurrentDateCommand } from 'Sieve/Extensions/rfc5260';
+import { SpamTestTest, VirusTestTest } from 'Sieve/Extensions/rfc5235';
+import { DateTest, CurrentDateTest } from 'Sieve/Extensions/rfc5260';
 import { AddHeaderCommand, DeleteHeaderCommand } from 'Sieve/Extensions/rfc5293';
 
 import {
@@ -72,6 +72,12 @@ import {
 	RejectCommand
 } from 'Sieve/Extensions/rfc5429';
 
+import {
+	MailboxExistsTest,
+	MetadataTest,
+	MetadataExistsTest
+} from 'Sieve/Extensions/rfc5490';
+
 import {
 	IncludeCommand,
 	ReturnCommand
@@ -92,42 +98,46 @@ const
 		keep: KeepCommand,
 		redirect: RedirectCommand,
 		// Test commands
-		address: AddressCommand,
-		allof: AllOfCommand,
-		anyof: AnyOfCommand,
-		envelope: EnvelopeCommand,
-		exists: ExistsCommand,
-		false: FalseCommand,
-		header: HeaderCommand,
-		not: NotCommand,
-		size: SizeCommand,
-		true: TrueCommand,
+		address: AddressTest,
+		allof: AllOfTest,
+		anyof: AnyOfTest,
+		envelope: EnvelopeTest,
+		exists: ExistsTest,
+		false: FalseTest,
+		header: HeaderTest,
+		not: NotTest,
+		size: SizeTest,
+		true: TrueTest,
 		// rfc5173
-		body: BodyCommand,
+		body: BodyTest,
 		// rfc5183
-		environment: EnvironmentCommand,
+		environment: EnvironmentTest,
 		// rfc5229
 		set: SetCommand,
-		string: StringCommand,
+		string: StringTest,
 		// rfc5230
 		vacation: VacationCommand,
 		// rfc5232
 		setflag: SetFlagCommand,
 		addflag: AddFlagCommand,
 		removeflag: RemoveFlagCommand,
-		hasflag: HasFlagCommand,
+		hasflag: HasFlagTest,
 		// rfc5235
-		spamtest: SpamTestCommand,
-		virustest: VirusTestCommand,
+		spamtest: SpamTestTest,
+		virustest: VirusTestTest,
 		// rfc5260
-		date: DateCommand,
-		currentdate: CurrentDateCommand,
+		date: DateTest,
+		currentdate: CurrentDateTest,
 		// rfc5293
 		AddHeaderCommand,
 		DeleteHeaderCommand,
 		// rfc5429
 		ereject: ErejectCommand,
 		reject: RejectCommand,
+		// rfc5490
+		mailboxexists: MailboxExistsTest,
+		metadata: MetadataTest,
+		metadataexists: MetadataExistsTest,
 		// rfc6609
 		include: IncludeCommand,
 		return: ReturnCommand
@@ -237,14 +247,14 @@ export const parseScript = (script, name = 'script.sieve') => {
 				new_command = new ConditionalCommand(value);
 			} else if (Commands[value]) {
 				if ('allof' === value || 'anyof' === value) {
-//					(command instanceof ConditionalCommand || command instanceof NotCommand) || error('Test-list not in conditional');
+//					(command instanceof ConditionalCommand || command instanceof NotTest) || error('Test-list not in conditional');
 				}
 				new_command = new Commands[value]();
 			} else {
 				console.error('Unknown command: ' + value);
 				if (command && (
 				    command instanceof ConditionalCommand
-				 || command instanceof NotCommand
+				 || command instanceof NotTest
 				 || command.tests instanceof GrammarTestList)) {
 					new_command = new GrammarTest(value);
 				} else {
@@ -253,7 +263,7 @@ export const parseScript = (script, name = 'script.sieve') => {
 			}
 
 			if (new_command instanceof GrammarTest) {
-				if (command instanceof ConditionalCommand || command instanceof NotCommand) {
+				if (command instanceof ConditionalCommand || command instanceof NotTest) {
 					// if/elsif/else new_command
 					// not new_command
 					command.test = new_command;
diff --git a/dev/Sieve/README.md b/dev/Sieve/README.md
index ec8173089..2e7e4946c 100644
--- a/dev/Sieve/README.md
+++ b/dev/Sieve/README.md
@@ -18,7 +18,7 @@ https://www.iana.org/assignments/sieve-extensions/sieve-extensions.xhtml
 - [x] RFC5429 ereject / reject
 - [ ] RFC5435 enotify
 - [ ] RFC5463 ihave
-- [ ] RFC5490 mailbox / mboxmetadata / servermetadata
+- [x] RFC5490 mailbox / mboxmetadata / servermetadata
 - [ ] RFC5703 enclose / extracttext / foreverypart / mime / replace
 - [ ] RFC6131 vacation-seconds
 - [ ] RFC6134 extlists
diff --git a/dev/Sieve/Tests.js b/dev/Sieve/Tests.js
index 70c2e2487..30949f0ed 100644
--- a/dev/Sieve/Tests.js
+++ b/dev/Sieve/Tests.js
@@ -18,7 +18,7 @@ const
 /**
  * https://tools.ietf.org/html/rfc5228#section-5.1
  */
-export class AddressCommand extends GrammarTest
+export class AddressTest extends GrammarTest
 {
 	constructor()
 	{
@@ -69,7 +69,7 @@ export class AddressCommand extends GrammarTest
 /**
  * https://tools.ietf.org/html/rfc5228#section-5.2
  */
-export class AllOfCommand extends GrammarTest
+export class AllOfTest extends GrammarTest
 {
 	constructor()
 	{
@@ -86,7 +86,7 @@ export class AllOfCommand extends GrammarTest
 /**
  * https://tools.ietf.org/html/rfc5228#section-5.3
  */
-export class AnyOfCommand extends GrammarTest
+export class AnyOfTest extends GrammarTest
 {
 	constructor()
 	{
@@ -103,7 +103,7 @@ export class AnyOfCommand extends GrammarTest
 /**
  * https://tools.ietf.org/html/rfc5228#section-5.4
  */
-export class EnvelopeCommand extends GrammarTest
+export class EnvelopeTest extends GrammarTest
 {
 	constructor()
 	{
@@ -141,7 +141,7 @@ export class EnvelopeCommand extends GrammarTest
 /**
  * https://tools.ietf.org/html/rfc5228#section-5.5
  */
-export class ExistsCommand extends GrammarTest
+export class ExistsTest extends GrammarTest
 {
 	constructor()
 	{
@@ -167,7 +167,7 @@ export class ExistsCommand extends GrammarTest
 /**
  * https://tools.ietf.org/html/rfc5228#section-5.6
  */
-export class FalseCommand extends GrammarTest
+export class FalseTest extends GrammarTest
 {
 	toString()
 	{
@@ -178,7 +178,7 @@ export class FalseCommand extends GrammarTest
 /**
  * https://tools.ietf.org/html/rfc5228#section-5.7
  */
-export class HeaderCommand extends GrammarTest
+export class HeaderTest extends GrammarTest
 {
 	constructor()
 	{
@@ -228,7 +228,7 @@ export class HeaderCommand extends GrammarTest
 /**
  * https://tools.ietf.org/html/rfc5228#section-5.8
  */
-export class NotCommand extends GrammarTest
+export class NotTest extends GrammarTest
 {
 	constructor()
 	{
@@ -250,7 +250,7 @@ export class NotCommand extends GrammarTest
 /**
  * https://tools.ietf.org/html/rfc5228#section-5.9
  */
-export class SizeCommand extends GrammarTest
+export class SizeTest extends GrammarTest
 {
 	constructor()
 	{
@@ -279,7 +279,7 @@ export class SizeCommand extends GrammarTest
 /**
  * https://tools.ietf.org/html/rfc5228#section-5.10
  */
-export class TrueCommand extends GrammarTest
+export class TrueTest extends GrammarTest
 {
 	toString()
 	{