@@ -, +, @@ 
    up anything to actually send messages on your test instance
---
 C4/Letters.pm                                 |  6 +++
 installer/data/mysql/mandatory/sysprefs.sql   |  1 +
 .../en/modules/admin/preferences/admin.pref   |  9 ++++
 t/db_dependent/Letters.t                      | 45 ++++++++++++++++++-
 4 files changed, 60 insertions(+), 1 deletion(-)
--- a/C4/Letters.pm	
+++ a/C4/Letters.pm	
@@ -1021,6 +1021,10 @@ sub SendQueuedMessages {
     Koha::Exceptions::BadParameter->throw("Parameter message_id cannot be empty if passed.")
         if ( exists( $params->{message_id} ) && !$params->{message_id} );
 
+    my $MessageQueueMode = C4::Context->preference('MessageQueueMode');
+
+    return 0 unless ( $MessageQueueMode eq 'on' || $MessageQueueMode eq 'plugin' );
+
     if ( C4::Context->config("enable_plugins") ) {
         my @plugins = Koha::Plugins->new->GetPlugins({
             method => 'before_send_messages',
@@ -1038,6 +1042,8 @@ sub SendQueuedMessages {
         }
     }
 
+    return 0 unless ( $MessageQueueMode eq 'on' );
+
     my $smtp_transports = {};
 
     my $count_messages = 0;
--- a/installer/data/mysql/mandatory/sysprefs.sql	
+++ a/installer/data/mysql/mandatory/sysprefs.sql	
@@ -411,6 +411,7 @@ INSERT INTO systempreferences ( `variable`, `value`, `options`, `explanation`, `
 ('MaxTotalSuggestions','',NULL,'Number of total suggestions used for time limit with NumberOfSuggestionDays','Free'),
 ('MembershipExpiryDaysNotice','',NULL,'Send an account expiration notice that a patron\'s card is about to expire after','Integer'),
 ('MergeReportFields','',NULL,'Displayed fields for deleted MARC records after merge','Free'),
+('MessageQueueMode','on','on|off|plugins','Search Engine','Choice'),
 ('minPasswordLength','8',NULL,'Specify the minimum length of a patron/staff password','free'),
 ('NewItemsDefaultLocation','','','If set, all new items will have a location of the given Location Code ( Authorized Value type LOC )',''),
 ('NewsAuthorDisplay','none','none|opac|staff|both','Display the author name for news items.','Choice'),
--- a/koha-tmpl/intranet-tmpl/prog/en/modules/admin/preferences/admin.pref	
+++ a/koha-tmpl/intranet-tmpl/prog/en/modules/admin/preferences/admin.pref	
@@ -301,3 +301,12 @@ Administration:
                 "ARRAY": "Searchable array"
             - <br>ISO2709 format is recommended as it is faster and takes less space, whereas array format makes the full MARC record searchable.
             - <br><strong>NOTE:</strong> Making the full record searchable may have a negative effect on relevance ranking of search results.
+    Message processing:
+        -
+            - "When running the message queue processor"
+            - pref: MessageQueueMode
+              default: on
+              choices:
+                on: process all messages and plugin hooks
+                plugins: process plugin hooks only
+                off: process nothing
--- a/t/db_dependent/Letters.t	
+++ a/t/db_dependent/Letters.t	
@@ -19,7 +19,7 @@ 
 
 use Modern::Perl;
 use File::Basename qw(dirname);
-use Test::More tests => 103;
+use Test::More tests => 104;
 
 use Test::MockModule;
 use Test::Warn;
@@ -1582,3 +1582,46 @@ subtest 'Quote user params in GetPreparedLetter' => sub {
         $exec_time
         );
 };
+
+subtest 'Test MessageQueueMode' => sub {
+    plan tests => 3;
+
+    my $dbh = C4::Context->dbh;
+
+    my $borrowernumber = Koha::Patron->new({
+        firstname    => 'Jane',
+        surname      => 'Smith',
+        categorycode => $patron_category,
+        branchcode   => $library->{branchcode},
+        dateofbirth  => $date,
+    })->store->borrowernumber;
+
+    $dbh->do(q|DELETE FROM message_queue|);
+    $my_message = {
+        'letter' => {
+            'content'      => 'a message',
+            'metadata'     => 'metadata',
+            'code'         => 'TEST_MESSAGE',
+            'content_type' => 'text/plain',
+            'title'        => 'message title'
+        },
+        'borrowernumber'         => $borrowernumber,
+        'to_address'             => undef,
+        'message_transport_type' => 'sms',
+        'from_address'           => 'from@example.com'
+    };
+
+    my $id = C4::Letters::EnqueueLetter($my_message);
+
+    t::lib::Mocks::mock_preference('MessageQueueMode', 'off');
+    C4::Letters::SendQueuedMessages();
+    is( Koha::Notice::Messages->find( $id )->status, 'pending', 'Message is pending for off' );
+
+    t::lib::Mocks::mock_preference('MessageQueueMode', 'plugin');
+    C4::Letters::SendQueuedMessages();
+    is( Koha::Notice::Messages->find( $id )->status, 'pending', 'Message is pending for plugin' );
+
+    t::lib::Mocks::mock_preference('MessageQueueMode', 'on');
+    C4::Letters::SendQueuedMessages();
+    is( Koha::Notice::Messages->find( $id )->status, 'failed', 'Message is failed for on' );
+};
--