diff --git a/src/services.js b/src/services.js
index 0cffa84b0..f57d25968 100644
--- a/src/services.js
+++ b/src/services.js
@@ -1088,7 +1088,7 @@ function setupSendMail(app, options, callback) {
             { 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_SMTP_STARTLS`, value: '1' },
+            { name: `${envPrefix}MAIL_SMTP_STARTTLS`, value: '1' },
         ];
         debugApp(app, 'Setting sendmail addon config to %j', env);
         appdb.setAddonConfig(app.id, 'sendmail', env, callback);