Is it possible for the Developer version of the Microsoft 365 to allow Email relays?

Tory Wilson 21 Reputation points

I need to test to see if an old software package of ours can send alert emails within our customer's network (the software is installed onsite), even if said customers only use Microsoft 365 as their email server. The software uses SMTP to send the email.

I have tried to just simply send emails to one of the dummy accounts (with and without using Basic Authentication, via a User explicitly created to send the emails), and received this error: "Mailbox unavailable. The server response was: Relay not permitted".

I attempted to follow the "Step-by-step instructions for direct send" in but I cannot make an MX Record (Only a TXT Record). All steps I can find to make a MX Record also require me to get data from the domain host... of which all of mine are the fake ones set up by the Developer account.

I attempted to create a Connection, but got this error "Error executing request. For this service offering, you can’t create or update inbound connectors in your organization" - Again, I'm just using the Developer version (the one with 15 fake user accounts for testing).

Again, my main goal is to show that if a customer of my company who buys and installs our software AND only uses Microsoft 365 can still receive emails sent out by that software. I'd personally prefer to use Direct Send as our customers are unlikely to need to the software to send the alert emails outside of their own domain.

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  1. Jame Xu-MSFT 4,171 Reputation points

    Hi @Tory Wilson ,
    Inbound connectors for mailflow are not supported in the Developer version of the Microsoft 365, so you could not test it. But after purchasing a standard subscription, you can follow the steps provided in the documentation:


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