For those developing integrations with Microsoft O365 you'll probably have come across the E5 Sandbox tenants. These are temporary tenants provided by Microsoft, full of plausible but fake users and data, specifically targeted at Developers. What if you want to send test calls into your voice app or auto attendant/call queue in an E5 Sandbox? It can be done!
Microsoft Teams Phone Resource Account in E5 Sandbox?
A known limitation in the E5 sandbox is that you can’t purchase any licenses on these tenants, even licenses that don’t cost anything such as the Microsoft Teams Phone Resource Account license. This is a problem for those of us developing Microsoft Teams integrations that might rely on receiving PSTN calls into voice bots.
You can connect and configure almost everything required to send in direct routing phone calls. You can create resource accounts. All the Powershell and Teams Admin Center (TAC) pieces are there. It’s just that pesky license that’s missing, stopping phone number assignment.
The Workaround
The good news is there is a workaround of sorts. I hadn’t seen this published anywhere else so wondered if it’s perhaps not widely known. The summary is send calls to a ‘standard’ user, then immediately forward to your voice bot resource account user.
Here’s a full step by step example:
Add a resource account ready for first or third party voice apps
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Make your resource account as usual. You can do this in TAC as long as it’s a standard auto attendant or call queue you’re after. If you want a custom app you’ll need Powershell to run New-CsOnlineApplicationInstance which lets you specify the third-party app GUID.
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Head to admin.microsoft.com and find your new resource user. Give it a full E5 license (you should have a bunch spare in your sandbox tenant).
Add a full blown E5 license to that user.
You might be thinking that’s sufficient, as that adds ‘Microsoft 365 Phone System’ as an enabled app to the resource user, but alas if you try to assign a phone number you’ll get an error like:
User '045a932e-0403-4ec1-9606-c06c12345678' lacks appropriate licenses to assign a 'DirectRouting' number.
So here we’ll try our workaround. Our target number in our case is
+18005550101. We’ll assign it to a standard user we aren’t using
for calls: Adele Vance (one of the pre-built test users). You can do
phone number assignment from TAC on the User’s settings page
Account tab.
Add a user redirect for all calls straight to your resource account user
After you’ve assigned the number navigate to the user’s Voice tab on the same page. From here you can configure calls to be immediately forwarded to a person and select your new resource account. This is the key step!
I think it’s the wording here that means this isn’t a well known workaround. ‘Person’ implies that standard users work but resource accounts will not. In fact any phone-enabled user (standard or resource account) can be selected.
And that’s it! Now you can send in calls via direct routing to your test number and have them route to auto attendants, call queues or third party apps in your E5 Sandbox tenant.
VoIP Toolbox - Helpful Teams Voice Tools
Build up a dashboard of test calls and test suites.
No soft phone or voice infra to run, just calls from the browser direct in to your Teams tenant as PSTN DR calls.
Enjoy workarounds like this? You might like VoIP Toolbox. It lets you test calls directly into any Teams tenant as PSTN Direct Routing calls. All right from your browser, without managing any voice infrastructure.
- Manual & Ad-Hoc Testing: Trigger calls directly from your browser, no softphones or local setup needed. Listen in live, save test templates, and access full SIP traces for instant troubleshooting.
- Automated Suites: Run scheduled calls for continuous uptime monitoring.
- CI/CD Integration: Fire off bulk call tests directly inside your build pipelines (DTMF navigation, clean tear-downs, etc.).
If that sounds useful, drop me a line at [email protected] and I can sort out a test account for you and your team.