diff --git a/lib/Migration/Version1100Date20210304143008.php b/lib/Migration/Version1100Date20210304143008.php
index 34f83ebdd4..f5dfc680fb 100644
--- a/lib/Migration/Version1100Date20210304143008.php
+++ b/lib/Migration/Version1100Date20210304143008.php
@@ -52,7 +52,8 @@ public function changeSchema(IOutput $output, Closure $schemaClosure, array $opt
 				'default' => false
 			]);
 			$tagsTable->setPrimaryKey(['id']);
-			$tagsTable->addIndex(['user_id'], 'mail_msg_tags_usr_id_index');
+			// Dropped in Version3600Date20240205180726 because mail_msg_tags_usr_id_index is redundant with mail_msg_tags_usr_lbl_idx
+			// $tagsTable->addIndex(['user_id'], 'mail_msg_tags_usr_id_index');
 			$tagsTable->addUniqueIndex(
 				[
 					'user_id',
diff --git a/lib/Migration/Version1130Date20220412111833.php b/lib/Migration/Version1130Date20220412111833.php
index 5851ce155f..e9de99ffb1 100644
--- a/lib/Migration/Version1130Date20220412111833.php
+++ b/lib/Migration/Version1130Date20220412111833.php
@@ -167,7 +167,9 @@ public function changeSchema(IOutput $output, Closure $schemaClosure, array $opt
 		// Add named indices
 		$messagesTable->addIndex(['mailbox_id', 'flag_important', 'flag_deleted', 'flag_seen'], 'mail_messages_id_flags');
 		$messagesTable->addIndex(['mailbox_id', 'flag_deleted', 'flag_flagged'], 'mail_messages_id_flags2');
-		$messagesTable->addIndex(['mailbox_id'], 'mail_messages_mailbox_id');
+		// Dropped in Version3600Date20240205180726 because mail_messages_mailbox_id is redundant with mail_messages_mb_id_uid
+		// $messagesTable->addIndex(['mailbox_id'], 'mail_messages_mailbox_id');
+
 		// mail_messages_msgid_idx was added later and may not exist until optional indices are created
 		$messagesTable->addIndex(
 			['message_id'],
diff --git a/lib/Migration/Version2300Date20221216115727.php b/lib/Migration/Version2300Date20221216115727.php
index c27b01916e..ae910d834d 100644
--- a/lib/Migration/Version2300Date20221216115727.php
+++ b/lib/Migration/Version2300Date20221216115727.php
@@ -67,7 +67,8 @@ public function changeSchema(IOutput $output, Closure $schemaClosure, array $opt
 			]);
 			$table->setPrimaryKey(['id'], 'mail_smime_certs_id_idx');
 			$table->addIndex(['user_id'], 'mail_smime_certs_uid_idx');
-			$table->addIndex(['id', 'user_id'], 'mail_smime_certs_id_uid_idx');
+			// Dropped in Version3600Date20240205180726
+			// $table->addIndex(['id', 'user_id'], 'mail_smime_certs_id_uid_idx');
 		}
 
 		return $schema;