Hello,

If I remember correctly outgoing port 25 on Azure is blocked by default to avoid SPAM being sent from their network. You should check if it is possible to unblock it as SmarterMail could not send outgoing mail if that's not the case.
https://docs.microsoft.com/en-us/azure/virtual-network/troubleshoot-outbound-smtp-connectivity 

Also I'm not sur if Azure Application Services give you access on a "real" virtual machine where you can install your own windows services. It looks to me that Application Services is to host web apps.

https://docs.microsoft.com/en-us/azure/app-service/overview 

However I have no knowledge about using Azure so maybe should would ask them about this or wait for advices from somebody else on here.

Kind regards