[Koha] Notice Email send error

Dear All, I am trying to send email notices; Using KOHA 21.11 and have configured the SMTP servers using the option in the Administration Module I have tried Gmail as well as our university email server hosted on zimbra; and both give error "Unhandled email failure, check the logs for further details" Where do look for these logs to identify the problem? Gmail Settings. Host: smtp.gmail.com Port: 587 Timeout:120s SSL: SSL Authentication: Yes (My gmail emal address and password) With best regards, Naveen Ali ITM-JE (EAKL) Inst Representative for HEC Digital Library Resources. NEDUET, Karachi.