Internal Relay with Office 365 connector

[fmsoliveir-cyber]

currently have an SMTP server on IIS running on Windows Server 2019 and a connector in Office 365 using the public IP to allow email sending as a mail relay, using only port 25 without authentication (for legacy applications). I installed Postal internally to replace this server, configured it on my public domain (xpto.com), and the public IP from the server is the same as the old server to keep everything normal, but it’s not working properly.

Specifically: it works for sending emails to my public domain (xpto.com), but it does not work for other domains (gmail.com, hotmail.com, etc.) because it gives a hard fail error:
550 5.7.64 TenantAttribution; Relay Access Denied [No TLS]

I did extensive testing and found that if the return_path_domain is set to xpto.com, I can send to external domains, but then I cannot send to my public domain (xpto.com)

What can I do to resolve this issue?

[willpower232]

I know they got pretty keen on certificates for connections, with Postal you have to configure that yourself.

Have you supplied a certificate and enabled tls?

postal/doc/config/yaml.yml

Lines 110 to 115 in 9c5f96a

	# Enable TLS for the SMTP server (requires certificate)
	tls_enabled: false
	# The path to the SMTP server's TLS certificate
	tls_certificate_path: $config-file-root/smtp.cert
	# The path to the SMTP server's TLS private key
	tls_private_key_path: $config-file-root/smtp.key