Hello @Luis Alfredo,
Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.
Azure only blocks outbound SMTP connections on TCP port 25 for few subscription types.
https://learn.microsoft.com/en-us/azure/virtual-network/troubleshoot-outbound-smtp-connectivity
Azure recommends using authenticated SMTP relay services to send email from Azure VMs or from Azure App Service. (These relay services typically connect through TCP port 587, but they support other ports.) Using these email delivery services isn't restricted in Azure, regardless of the subscription type.
I checked the logs and can see that port 456 is open. The TLS handshake is happening just fine, and I can also see some encrypted Application data being transferred. But then there is a TCP reset at the end (I believe sent by the application). It looks like an application issue.
I would request you to check the application for any issues and further troubleshooting.
Regards,
Gita