O365 Relay Issue

[ITGURU]

I have a local IIS virtual SMTP Server setup so that my monitoring systems and local systems can send emails when required.

It it setup to relay to my 365 domain using the mydomain.mail.protection.outlook.com

 

Everything works as expected when the recipient is on the same domain.

 

If i try and get any of the systems to email any other external domain, the email is never received.

 

Please could someone help me out with what setting i have missed for relaying emails to any domain.

 

Thank you.

[HPlum78]

I have a change for this very service to go live next week, have you setup any connectors in exchange online? How are you accepting SMTP submissions on you box un auth and authenticate?

[ITGURU]

I have a change for this very service to go live next week, have you setup any connectors in exchange online? How are you accepting SMTP submissions on you box un auth and authenticate?

 

No i haven't - emails to same domain work fine just not to others that are external.

 

let me know how you get on

[HPlum78]

https://docs.microsoft.com/en-us/exchange/mail-flow-best-practices/how-to-set-up-a-multifunction-device-or-application-to-send-email-using-office-3

 

So you need opt 3 as you want to send to external rcpts

[ITGURU]

https://docs.microsoft.com/en-us/exchange/mail-flow-best-practices/how-to-set-up-a-multifunction-device-or-application-to-send-email-using-office-3

 

So you need opt 3 as you want to send to external rcpts

Yeah already got that in place - emails on same domain work through the IIS SMTP server, but all other domain get stuck in the local inetpub\mailroot\queue folder

[HPlum78]

oh i see so not leaving the IIS box...

[ITGURU]

Looks like after the config changes a restart of the service doesnt enable the settings - after an iisreset it then works to external domains!

 

All sorted I think, testing to commence.

[HPlum78]

Yeah the config for this is from the old version of IIS and I have been caught out with that same issue more than once... in fact i have just added our data centre subnets to the allowed list in the config and then decided to manage what is allowed into the box using Windows Firewall so I don't have to remember to do just that, also I have multiple nodes behind a Load Balancer so each change was multiple changes to the backend nodes (and no PowerShell!).