It seams Xeams does not bounce email sent to non existing user/email?

Please ensure the settings for NDR are correctly set up. Go to Server Configuration/SMTP Configuration and click the Advanced tab.

If the values are set up correctly, send us more details about the mail flow. We need to know:

• Is the message being sent out or coming in?
• Is it being sent by a valid user in Xeams?

Only NDR is checked in the Non-delivery Report section

I have sent to non existing user on the xeams and didn't get bounce message.

Just to clarify, you sent an email from (example @gmail.com) to invalid.user@yourcompany.com. In that case, the NDR will NOT be generated by Xeams but @gmail.com. NDRs are generated by the SMTP server that accepts the message. Consider the following example:

                    1                    2
User ------> User's SMTP Server -----> Xeams
       ✔                         ✖       

Two SMTP servers are involved: 1 and 2 (Xeams). In this case, the user's SMTP server accepts the message but not Xeams. Therefore, generating an NDR is the responsibility of server 1, not 2.

Check SMTPConversation.log to confirm an incoming email was rejected by Xeams. Search for the sender's email address to locate the log entries.