Exchange 2010 Receive Connector

I have an external service that will be relaying through our Exchange environment. IT will be sending to both internal and external recipients.  The service is configured for SMTP authentication over port 587.

My settings on the connector are TLS and Externally secure for authentication tab and Exchnage Servers for Permission tab.

However it fails when testing on the external service end and when i check the SMTP Receive logs in only see the below.

SMTPSubmit SMTPAcceptAnyRecipient SMTPAcceptAuthenticationFlag SMTPAcceptAnySender SMTPAcceptAuthoritativeDomainSender BypassAntiSpam BypassMessageSizeLimit SMTPAcceptEXCH50 AcceptRoutingHeaders
220 Servername Microsoft ESMTP MAIL Service ready at Fri, 10 Apr 2020 11:11:09 -0400
EHLO f23afa3dd522
250-servername Hello [x,x,x,x]
250-SIZE 27262976
250-PIPELINING
250-DSN
250-ENHANCEDSTATUSCODES
250-AUTH
250-8BITMIME
250-BINARYMIME
250-CHUNKING
250-XEXCH50
250 XSHADOW

The session disconnects after that.

It's been a while when i've had to setup something similar to this, so i want to make sure my configuration is correct.

Thanks in advance.