Hi @mzislam , Kindly find the following documentation related to mail sender parameter configuration.

Hope the documentation helps you.

Kind Regards,

Vinu.

DEFAULT_MAIL_SENDER wouldn't reflect anywhere if your application is configured with a mailbox user and your email server need user authentication to send emails. But you need to have a value here as null is not accepting. Default is connect@localhost

but for the companies which allow anonymous email sending from the email servers you may specify a dummy address here something similar to noreply@yourdomain.com 

then recipients will receive something like this

@Ruchira ,I am getting the below errors in Applications Messages window:

Error while sending data... 
Caused by: com.sun.mail.util.MailConnectException: Couldn't connect to host, port: mail.i*****oup.com, 465; timeout 60000 
Caused by: java.net.UnknownHostException: mail.i*****oup.com

@mzislam This error should be connected to incorrect configurations of the mail server or a port blocking due to strict firewall configs. Good to check if mail server can be reachable from the MWS from the port configured