diff --git a/app/models/global_setting.rb b/app/models/global_setting.rb
index f6eed5da52..571dce2bd2 100644
--- a/app/models/global_setting.rb
+++ b/app/models/global_setting.rb
@@ -272,6 +272,7 @@
         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_force_tls && GlobalSetting.smtp_enable_start_tls,
         open_timeout: GlobalSetting.smtp_open_timeout.to_f,
         read_timeout: GlobalSetting.smtp_read_timeout.to_f,