However, when I see the screenshot there is something listening on port 25 which I think is postfix, is the smtp relay postfix on the same host of the Wazuh Server or is it on a different host?
I was checking again your first screenshot and I noticed you have a domain in <smtp_server> , let's try changing that value to localhost, change that line for <smtp_server>localhost</smtp_server>
Try that way before making any change on postfix, also if you are still not receiving email alerts, share the /var/ossec/logs/ossec.log and /var/log/maillog for me to take a look
I changed the port that the localhost listens to 9025 and I was not successful, I am attaching what you requested