diff --git a/data/web/inc/functions.mailbox.inc.php b/data/web/inc/functions.mailbox.inc.php
index d53cda9aef..57fd8b022c 100644
--- a/data/web/inc/functions.mailbox.inc.php
+++ b/data/web/inc/functions.mailbox.inc.php
@@ -2837,6 +2837,7 @@ function mailbox($_action, $_type, $_data = null, $_extra = null) {
                 ':domain' => $domain
               ));
               // save tags
+              $tags_changed = false;
               foreach($tags as $index => $tag){
                 if (empty($tag)) continue;
                 if ($index > $GLOBALS['TAGGING_LIMIT']) {
@@ -2852,6 +2853,13 @@ function mailbox($_action, $_type, $_data = null, $_extra = null) {
                   ':domain' => $domain,
                   ':tag_name' => $tag,
                 ));
+                if ($stmt->rowCount() > 0) $tags_changed = true;
+              }
+              // tags are stored in a separate table, so adding one does not touch
+              // `domain` and its `modified` ON UPDATE column never fires
+              if ($tags_changed) {
+                $stmt = $pdo->prepare("UPDATE `domain` SET `modified` = NOW() WHERE `domain` = :domain");
+                $stmt->execute(array(':domain' => $domain));
               }
 
               $_SESSION['return'][] = array(
@@ -3005,6 +3013,7 @@ function mailbox($_action, $_type, $_data = null, $_extra = null) {
                 ':domain' => $domain
               ));
               // save tags
+              $tags_changed = false;
               foreach($tags as $index => $tag){
                 if (empty($tag)) continue;
                 if ($index > $GLOBALS['TAGGING_LIMIT']) {
@@ -3020,6 +3029,13 @@ function mailbox($_action, $_type, $_data = null, $_extra = null) {
                   ':domain' => $domain,
                   ':tag_name' => $tag,
                 ));
+                if ($stmt->rowCount() > 0) $tags_changed = true;
+              }
+              // tags are stored in a separate table, so adding one does not touch
+              // `domain` and its `modified` ON UPDATE column never fires
+              if ($tags_changed) {
+                $stmt = $pdo->prepare("UPDATE `domain` SET `modified` = NOW() WHERE `domain` = :domain");
+                $stmt->execute(array(':domain' => $domain));
               }
 
               $_SESSION['return'][] = array(
@@ -3479,6 +3495,7 @@ function mailbox($_action, $_type, $_data = null, $_extra = null) {
               ));
             }
             // save tags
+            $tags_changed = false;
             foreach($tags as $index => $tag){
               if (empty($tag)) continue;
               if ($index > $GLOBALS['TAGGING_LIMIT']) {
@@ -3495,9 +3512,16 @@ function mailbox($_action, $_type, $_data = null, $_extra = null) {
                   ':username' => $username,
                   ':tag_name' => $tag,
                 ));
+                if ($stmt->rowCount() > 0) $tags_changed = true;
               } catch (Exception $e) {
               }
             }
+            // tags are stored in a separate table, so adding one does not touch
+            // `mailbox` and its `modified` ON UPDATE column never fires
+            if ($tags_changed) {
+              $stmt = $pdo->prepare("UPDATE `mailbox` SET `modified` = NOW() WHERE `username` = :username");
+              $stmt->execute(array(':username' => $username));
+            }
 
             $_SESSION['return'][] = array(
               'type' => 'success',
@@ -6273,6 +6297,7 @@ function mailbox($_action, $_type, $_data = null, $_extra = null) {
               return false;
             }
 
+            $tags_changed = false;
             foreach($tags as $tag){
               // delete tag
               $wasModified = true;
@@ -6281,6 +6306,13 @@ function mailbox($_action, $_type, $_data = null, $_extra = null) {
                 ':domain' => $domain,
                 ':tag_name' => $tag,
               ));
+              if ($stmt->rowCount() > 0) $tags_changed = true;
+            }
+            // tags are stored in a separate table, so removing one does not touch
+            // `domain` and its `modified` ON UPDATE column never fires
+            if ($tags_changed) {
+              $stmt = $pdo->prepare("UPDATE `domain` SET `modified` = NOW() WHERE `domain` = :domain");
+              $stmt->execute(array(':domain' => $domain));
             }
           }
 
@@ -6325,6 +6357,7 @@ function mailbox($_action, $_type, $_data = null, $_extra = null) {
             }
 
             // delete tags
+            $tags_changed = false;
             foreach($tags as $tag){
               $wasModified = true;
 
@@ -6333,6 +6366,13 @@ function mailbox($_action, $_type, $_data = null, $_extra = null) {
                 ':username' => $username,
                 ':tag_name' => $tag,
               ));
+              if ($stmt->rowCount() > 0) $tags_changed = true;
+            }
+            // tags are stored in a separate table, so removing one does not touch
+            // `mailbox` and its `modified` ON UPDATE column never fires
+            if ($tags_changed) {
+              $stmt = $pdo->prepare("UPDATE `mailbox` SET `modified` = NOW() WHERE `username` = :username");
+              $stmt->execute(array(':username' => $username));
             }
           }