Missing "Not deliverable" Mail with wrong E-Mail address

Hello Community,

I’m running HestiaCP on oracle cloud with standard roundcube and exim4 mailserver.

Sending and receiving mails are working fine.

But I have this issue:
When I send an email from HestiaCP/Roundcube to an address that does not exist (e.g. @gmx.com), I do not get any info back.
When I send an mail with Gmail to the not existing address, I receive the “Not deliverable” mail.

What could be the problem? Is there anything extra that needs to be set here to receive mails on not deliverable?

Thanks for help

Oracle cloud blocks by default port 25

Use a smtp relay…

Sorry, I send you the wrong infos: I use Sendinblue as SMTP relay.

Sending Mails to an correct E-Mail address is not the problem. But when I made an spelling misstake and the address don’t exist on the receiving server I don’t get back an “Not deliverable” Mail.

It is the task of Sendinblue to notify you if there are issues with delivery.