diff --git a/dev/Sieve/Commands.js b/dev/Sieve/Commands.js
index 79bf31849..4214849ba 100644
--- a/dev/Sieve/Commands.js
+++ b/dev/Sieve/Commands.js
@@ -73,7 +73,7 @@ export class RequireCommand extends GrammarCommand
 
 	toString()
 	{
-		return 'require ' + this.capabilities.toString() + ';';
+		return 'require ' + this.capabilities + ';';
 	}
 
 	pushArguments(args)
@@ -109,12 +109,12 @@ export class FileIntoCommand extends GrammarCommand
 
 	toString()
 	{
-		return 'fileinto '
+		return 'fileinto'
 			// https://datatracker.ietf.org/doc/html/rfc3894
-			+ ((this.copy && capa.includes('copy')) ? ':copy ' : '')
+			+ ((this.copy && capa.includes('copy')) ? ' :copy' : '')
 			// https://datatracker.ietf.org/doc/html/rfc5490#section-3.2
-			+ ((this.create && capa.includes('mailbox')) ? ':create ' : '')
-			+ this._mailbox
+			+ ((this.create && capa.includes('mailbox')) ? ' :create' : '')
+			+ ' ' + this._mailbox
 			+ ';';
 	}
 
@@ -150,10 +150,13 @@ export class RedirectCommand extends GrammarCommand
 
 	toString()
 	{
-		return 'redirect '
+
+		return 'redirect'
+			// https://datatracker.ietf.org/doc/html/rfc6134#section-2.3
+//			+ ((this.list && capa.includes('extlists')) ? ' :list ' + this.list : '')
 			// https://datatracker.ietf.org/doc/html/rfc3894
-			+ ((this.copy && capa.includes('copy')) ? ':copy ' : '')
-			+ this._address
+			+ ((this.copy && capa.includes('copy')) ? ' :copy' : '')
+			+ ' ' + this._address
 			+ ';';
 	}
 
diff --git a/dev/Sieve/Extensions/rfc5173.js b/dev/Sieve/Extensions/rfc5173.js
index 31b299053..5d85fdab6 100644
--- a/dev/Sieve/Extensions/rfc5173.js
+++ b/dev/Sieve/Extensions/rfc5173.js
@@ -25,7 +25,7 @@ export class BodyTest extends GrammarTest
 			+ (this.comparator ? ' :comparator ' + this.comparator : '')
 			+ ' ' + this.match_type
 			+ ' ' + this.body_transform
-			+ ' ' + this.key_list.toString();
+			+ ' ' + this.key_list;
 	}
 
 	pushArguments(args)
diff --git a/dev/Sieve/Extensions/rfc5183.js b/dev/Sieve/Extensions/rfc5183.js
index 1279f1f48..66d8cbe44 100644
--- a/dev/Sieve/Extensions/rfc5183.js
+++ b/dev/Sieve/Extensions/rfc5183.js
@@ -25,7 +25,7 @@ export class EnvironmentTest extends GrammarTest
 			+ (this.comparator ? ' :comparator ' + this.comparator : '')
 			+ ' ' + this.match_type
 			+ ' ' + this.name
-			+ ' ' + this.key_list.toString();
+			+ ' ' + this.key_list;
 	}
 
 	pushArguments(args)
diff --git a/dev/Sieve/Extensions/rfc5229.js b/dev/Sieve/Extensions/rfc5229.js
index 08b4aea8e..86e1b7df6 100644
--- a/dev/Sieve/Extensions/rfc5229.js
+++ b/dev/Sieve/Extensions/rfc5229.js
@@ -59,8 +59,8 @@ export class StringTest extends GrammarTest
 		return 'string'
 			+ ' ' + this.match_type
 			+ (this.comparator ? ' :comparator ' + this.comparator : '')
-			+ ' ' + this.source.toString()
-			+ ' ' + this.key_list.toString();
+			+ ' ' + this.source
+			+ ' ' + this.key_list;
 	}
 
 	pushArguments(args)
diff --git a/dev/Sieve/Extensions/rfc5230.js b/dev/Sieve/Extensions/rfc5230.js
index 1b077eb5c..a02670453 100644
--- a/dev/Sieve/Extensions/rfc5230.js
+++ b/dev/Sieve/Extensions/rfc5230.js
@@ -46,7 +46,7 @@ export class VacationCommand extends GrammarCommand
 //			result += ' :from ' + this.arguments[':from'];
 		}
 		if (this.addresses.length) {
-			result += ' :addresses ' + this.addresses.toString();
+			result += ' :addresses ' + this.addresses;
 		}
 		if (this.mime) {
 			result += ' :mime';
diff --git a/dev/Sieve/Extensions/rfc5232.js b/dev/Sieve/Extensions/rfc5232.js
index 3e5f378e3..918c944df 100644
--- a/dev/Sieve/Extensions/rfc5232.js
+++ b/dev/Sieve/Extensions/rfc5232.js
@@ -23,7 +23,7 @@ class FlagCommand extends GrammarCommand
 
 	toString()
 	{
-		return this.identifier + ' ' + this._variablename + ' ' + this.list_of_flags.toString() + ';';
+		return this.identifier + ' ' + this._variablename + ' ' + this.list_of_flags + ';';
 	}
 
 	get variablename()
@@ -79,8 +79,8 @@ export class HasFlagTest extends GrammarTest
 		return 'hasflag'
 			+ ' ' + this.match_type
 			+ (this.comparator ? ' :comparator ' + this.comparator : '')
-			+ ' ' + this.variable_list.toString()
-			+ ' ' + this.list_of_flags.toString();
+			+ ' ' + this.variable_list
+			+ ' ' + this.list_of_flags;
 	}
 
 	pushArguments(args)
diff --git a/dev/Sieve/Extensions/rfc5260.js b/dev/Sieve/Extensions/rfc5260.js
index 5c7868adc..57980f56f 100644
--- a/dev/Sieve/Extensions/rfc5260.js
+++ b/dev/Sieve/Extensions/rfc5260.js
@@ -36,7 +36,7 @@ export class DateTest extends GrammarTest
 			+ ' ' + this.match_type
 			+ ' ' + this.header_name
 			+ ' ' + this.date_part
-			+ ' ' + this.key_list.toString();
+			+ ' ' + this.key_list;
 	}
 
 	pushArguments(args)
@@ -77,7 +77,7 @@ export class CurrentDateTest extends GrammarTest
 			+ (this.comparator ? ' :comparator ' + this.comparator : '')
 			+ ' ' + this.match_type
 			+ ' ' + this.date_part
-			+ ' ' + this.key_list.toString();
+			+ ' ' + this.key_list;
 	}
 
 	pushArguments(args)
diff --git a/dev/Sieve/Extensions/rfc5490.js b/dev/Sieve/Extensions/rfc5490.js
index aa836c813..ca02aeb47 100644
--- a/dev/Sieve/Extensions/rfc5490.js
+++ b/dev/Sieve/Extensions/rfc5490.js
@@ -56,7 +56,7 @@ export class MetadataTest extends GrammarTest
 			+ (this.comparator ? ' :comparator ' + this.comparator : '')
 			+ ' ' + this.mailbox
 			+ ' ' + this.annotation_name
-			+ ' ' + this.key_list.toString();
+			+ ' ' + this.key_list;
 	}
 
 	pushArguments(args)
@@ -115,7 +115,7 @@ export class ServerMetadataTest extends GrammarTest
 			+ ' ' + this.match_type
 			+ (this.comparator ? ' :comparator ' + this.comparator : '')
 			+ ' ' + this.annotation_name
-			+ ' ' + this.key_list.toString();
+			+ ' ' + this.key_list;
 	}
 
 	pushArguments(args)
diff --git a/dev/Sieve/Extensions/rfc6134.js b/dev/Sieve/Extensions/rfc6134.js
new file mode 100644
index 000000000..f3558ad17
--- /dev/null
+++ b/dev/Sieve/Extensions/rfc6134.js
@@ -0,0 +1,32 @@
+/**
+ * https://tools.ietf.org/html/rfc6134
+ */
+
+import {
+	GrammarStringList,
+	GrammarTest
+} from 'Sieve/Grammar';
+
+/**
+ * https://datatracker.ietf.org/doc/html/rfc6134#section-2.7
+ */
+export class ValidExtListTest extends GrammarTest
+{
+	constructor()
+	{
+		super();
+		this.ext_list_names = new GrammarStringList;
+	}
+
+	get require() { return 'foreverypart'; }
+
+	toString()
+	{
+		return 'valid_ext_list ' + this.ext_list_names;
+	}
+
+	pushArguments(args)
+	{
+		this.ext_list_names = args.pop();
+	}
+}
diff --git a/dev/Sieve/Grammar.js b/dev/Sieve/Grammar.js
index b656b3ca8..102fb6cfa 100644
--- a/dev/Sieve/Grammar.js
+++ b/dev/Sieve/Grammar.js
@@ -70,7 +70,7 @@ export class GrammarCommand
 			result += ' ' + arrayToString(this.arguments, ' ');
 		}
 		return result + (
-			this.commands.length ? ' ' + this.commands.toString() : ';'
+			this.commands.length ? ' ' + this.commands : ';'
 		);
 	}
 
@@ -240,6 +240,12 @@ export class GrammarTest
 
 	toString()
 	{
+/*
+		// https://datatracker.ietf.org/doc/html/rfc6134#section-2.3
+		if (':list' == this.match_type && !capa.includes('extlists')) {
+			throw 'Unsupported match-type ' + this.match_type;
+		}
+*/
 		return (this.identifier
 			+ (this.comparator ? ' :comparator ' + this.comparator : '')
 			+ (this.match_type ? ' ' + this.match_type : '')
diff --git a/dev/Sieve/Parser.js b/dev/Sieve/Parser.js
index f64f037ae..0516fffa3 100644
--- a/dev/Sieve/Parser.js
+++ b/dev/Sieve/Parser.js
@@ -213,6 +213,10 @@ export const parseScript = (script, name = 'script.sieve') => {
 		pushArg = arg => {
 			command || error('Argument not part of command');
 			let prev_arg = args[args.length-1];
+/*
+			// https://datatracker.ietf.org/doc/html/rfc6134#section-2.3
+			if (':is' === arg || ':contains' === arg || ':matches' === arg || (capa.includes('extlists') && ':list')) {
+*/
 			if (':is' === arg || ':contains' === arg || ':matches' === arg) {
 				command.match_type = arg;
 			} else if (':value' === prev_arg || ':count' === prev_arg) {
diff --git a/dev/Sieve/README.md b/dev/Sieve/README.md
index e1988527f..4b4849acb 100644
--- a/dev/Sieve/README.md
+++ b/dev/Sieve/README.md
@@ -19,7 +19,7 @@ https://www.iana.org/assignments/sieve-extensions/sieve-extensions.xhtml
 - [x] RFC5435 enotify
 - [x] RFC5463 ihave
 - [x] RFC5490 mailbox / mboxmetadata / servermetadata
-- [ ] RFC5703 enclose / extracttext / foreverypart / mime / replace
+- [x] RFC5703 enclose / extracttext / foreverypart / mime / replace
 - [x] RFC6131 vacation-seconds
 - [ ] RFC6134 extlists
 - [ ] RFC6558 convert
diff --git a/dev/Sieve/Tests.js b/dev/Sieve/Tests.js
index dbd35837f..0397b5478 100644
--- a/dev/Sieve/Tests.js
+++ b/dev/Sieve/Tests.js
@@ -71,8 +71,8 @@ export class AddressTest extends GrammarTest
 			+ (this.comparator ? ' :comparator ' + this.comparator : '')
 			+ ' ' + this.address_part
 			+ ' ' + this.match_type
-			+ ' ' + this.header_list.toString()
-			+ ' ' + this.key_list.toString();
+			+ ' ' + this.header_list
+			+ ' ' + this.key_list;
 	}
 
 	pushArguments(args)
@@ -108,7 +108,7 @@ export class AllOfTest extends GrammarTest
 
 	toString()
 	{
-		return 'allof ' + this.tests.toString();
+		return 'allof ' + this.tests;
 	}
 }
 
@@ -125,7 +125,7 @@ export class AnyOfTest extends GrammarTest
 
 	toString()
 	{
-		return 'anyof ' + this.tests.toString();
+		return 'anyof ' + this.tests;
 	}
 }
 
@@ -150,8 +150,8 @@ export class EnvelopeTest extends GrammarTest
 			+ (this.comparator ? ' :comparator ' + this.comparator : '')
 			+ ' ' + this.address_part
 			+ ' ' + this.match_type
-			+ ' ' + this.envelope_part.toString()
-			+ ' ' + this.key_list.toString();
+			+ ' ' + this.envelope_part
+			+ ' ' + this.key_list;
 	}
 
 	pushArguments(args)
@@ -195,7 +195,7 @@ export class ExistsTest extends GrammarTest
 				result += ' :anychild';
 			}
 		}
-		return result + ' ' + this.header_names.toString();
+		return result + ' ' + this.header_names;
 	}
 
 	pushArguments(args)
@@ -281,8 +281,8 @@ export class HeaderTest extends GrammarTest
 //			+ (this.last ? ' :last' : (this.index.value ? ' :index ' + this.index : ''))
 			+ (this.comparator ? ' :comparator ' + this.comparator : '')
 			+ ' ' + this.match_type
-			+ ' ' + this.header_names.toString()
-			+ ' ' + this.key_list.toString();
+			+ ' ' + this.header_names
+			+ ' ' + this.key_list;
 	}
 
 	pushArguments(args)