SMTP defer on Sophos XGS 126

Hello,

I'm experiencing an issue where I cannot send email notifications from the Sophos XGS 126 router. The emails remain in the spool folder.

from log files

2024-02-12 14:26:00.736Z [4965] 1xZrDX-8Lgj0V-JN == support@s***.si R=router_for_notifications T=notification_smtp defer (-54) DT=0.000s: retry time not reached for any host for 's***.si'
2024-02-12 14:26:00.739Z [4967] nJjqWk-M4n4oB-Ma == support@s***.si R=router_for_notifications T=notification_smtp defer (-54) DT=0.000s: retry time not reached for any host for 's***.si'

I don't know what else I can do? Thank you for your help.