diff --git a/src/addons.js b/src/addons.js
index 17a609d82..3945c4c70 100644
--- a/src/addons.js
+++ b/src/addons.js
@@ -1023,7 +1023,7 @@ function setupEmail(app, options, callback) {
             { name: `${envPrefix}MAIL_SIEVE_PORT`, value: '4190' },
             { name: `${envPrefix}MAIL_DOMAIN`, value: app.domain },
             { name: `${envPrefix}MAIL_DOMAINS`, value: mailInDomains },
-            { name: 'MAIL_SERVER_HOST', value: settings.mailFqdn() },
+            { name: 'CLOUDRON_MAIL_SERVER_HOST', value: settings.mailFqdn() },
             { name: `${envPrefix}LDAP_MAILBOXES_BASE_DN`, value: 'ou=mailboxes,dc=cloudron' }
         ];