diff --git a/src/infra_version.js b/src/infra_version.js
index 22c9219bf..56badd31d 100644
--- a/src/infra_version.js
+++ b/src/infra_version.js
@@ -6,7 +6,7 @@
 
 exports = module.exports = {
     // a version change recreates all containers with latest docker config
-    'version': '48.18.0',
+    'version': '48.19.0',
 
     'baseImages': [
         { repo: 'cloudron/base', tag: 'cloudron/base:3.0.0@sha256:455c70428723e3a823198c57472785437eb6eab082e79b3ff04ea584faf46e92' }
diff --git a/src/services.js b/src/services.js
index 8b4cfadd8..55462cc20 100644
--- a/src/services.js
+++ b/src/services.js
@@ -1084,7 +1084,8 @@ function setupSendMail(app, options, callback) {
             { name: `${envPrefix}MAIL_SMTP_USERNAME`, value: app.mailboxName + '@' + app.mailboxDomain },
             { name: `${envPrefix}MAIL_SMTP_PASSWORD`, value: password },
             { name: `${envPrefix}MAIL_FROM`, value: app.mailboxName + '@' + app.mailboxDomain },
-            { name: `${envPrefix}MAIL_DOMAIN`, value: app.mailboxDomain }
+            { name: `${envPrefix}MAIL_DOMAIN`, value: app.mailboxDomain },
+            { name: `${envPrefix}MAIL_SMTP_STARTLS`, value: '1' },
         ];
         debugApp(app, 'Setting sendmail addon config to %j', env);
         appdb.setAddonConfig(app.id, 'sendmail', env, callback);