diff --git a/app/models/global_setting.rb b/app/models/global_setting.rb
index 6e06e18039..b2bef31fe2 100644
--- a/app/models/global_setting.rb
+++ b/app/models/global_setting.rb
@@ -255,6 +255,7 @@ class GlobalSetting
         domain: GlobalSetting.smtp_domain,
         user_name: GlobalSetting.smtp_user_name,
         password: GlobalSetting.smtp_password,
+        ca_file: "/etc/ssl/certs/ca-certificates.crt",
         enable_starttls_auto: GlobalSetting.smtp_enable_start_tls,
         open_timeout: GlobalSetting.smtp_open_timeout,
         read_timeout: GlobalSetting.smtp_read_timeout,