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How to make and receive calls around the world with Microsoft Phone System?


Microsoft offers enterprise voice capabilities both for internal communication within the organization, and for calling externally to any device or landline irrespective of location.

Employees’ expectations about the voice are changing. Voice remains a critical and essential workload as people report that 80 % of their time at work is spent collaborating (i.e. in meetings, calls). But how do you capture important information in voice? Typing at a PC or making analog recordings don’t meet the expectations anymore. Microsoft is delivering voice with things like transcription and translation. So, when you missed the meeting and try to figure out if the boss talked about you, you can literally ask Office 365, if your name was mentioned, and it’ll search through the meeting file, coming back with the results you needed. Instead of listening the meeting recording for 75 minutes, you can spend five minutes doing a little search in Office 365. Isn’t it awesome?

Now let’s hop in and start by explaining how the Phone System works.

What is Phone System and what features it provides?

For better understanding of Office 365 Phone System let’s take a look at the elements of a traditional telephone system within an organization, or Private Branch Exchange (PBX).

Traditional PBX deployment consists of three parts: the endpoints for employees to place and receive calls, the PBX connecting calls between internal users, as well as sending them to external users, and the PSTN (Public Switched Telephone Network) with all the external users. Phone System in Office 365 has the exact same building blocks. Every Teams client, whether it’s Windows, Mac, Web (currently Edge only), iOS, Android or IP phones, can be an endpoint and use PBX features in addition to other Teams features, that you know and love.

Phone System is completely cloud- and software-based, so you may start replacing hardware in your infrastructure and getting rid of PBX servers, saving money and moving everything in one single place. This is especially relevant for customers who are multi-national and have vendor by country for the PBXs. With the Phone System these organizations can centralize the software, increase its availability, and develop a uniform approach to management.

How you can connect the Phone System to the PSTN

Going back to our anatomy of the traditional phone deployment, we are now looking at the trunk portion. Connections between your PBX and PSTN are made through either Calling plan or Direct Routing (or mix of both).

Calling Plans

It’s Microsoft’s white-glove approach to PSTN availability in your tenant. In other words, PSTN connectivity is provided directly by Microsoft, so you have a single contract for all the features, including PSTN calling, and a single party to deal with. Microsoft partners in the backend take care of the PSTN trunks, but you never see that partner. The exceptions are Australia and Japan where third parties provide calling plans, but they are very tightly integrated with Microsoft.

In terms of compliance, Calling Plans meet all the legal requirements in the participating countries, the list of which is limited to countries where Microsoft operates as a regulated utility. Now, these include United States, United Kingdom, Spain, Netherlands, Puerto Rico, Ireland, Germany, France, Canada, Belgium. Australia and Japan are a little bit special case, where you get calling plans, but third parties (Telstra in Australia, and Softbank in Japan) are providing the calling plan features. This list is constantly being updated, so check it here .

This PSTN connection solution is completely cloud-based and doesn’t require any infrastructure on-premises. Phone numbers can be requested from Microsoft or brought in from your current provider.

Licensing model offers different management options. You can give a bunch of people in a building a license for a year, and then, if you change the operation, you can easily redeploy those licenses to other folks. For users calling only domestically, you can go for the cheaper domestic calling plan. For other users, calling internationally, you can get international calling, mixing and matching these as required.

Direct Routing

Essentially, this option brings your trunks to the party. Office 365 will be connected to the customer infrastructure, letting you use your existing PBX or your existing carrier contracts. Also, there’s no need to port any phone numbers since you’ll remain in the same pool of phone numbers.

On the very right side of the picture above, the user is being connected to the Phone System. It is, in its turn, connected over the Internet to the session border controller (SBC) on-premises, certified by Microsoft, which is the key component. The SBC might be connected to an existing PBX or some third-party voice apps (supported by the certified SBC partners). Over the voice trunk, SBC is connected to the PSTN provider.

This is a simplified architecture. A vast majority of deployments won’t look like this. Every company is different, and you might want to engage a partner to host the SBC, so you can get into a zero-hardware deployment in your company. You might also feel that nobody can do it better and cheaper than you in house. Whatever setup you choose, it’s just important that it’s connected to a certified session border controller.

Calling Plans and Direct Routing doesn’t exclude one another, you can mix these options to understand what makes the most sense for you.

Services and voicemail

Calls tab on the navigation rail in the Teams client opens up all the calling functionality. The picture below highlights some of the features of the Phone System. On the default page, you can find your own phone number (very useful in case you ever wonder how people can call you) and use a dial pad (or just type the digits from the keyboard). The upper menu contains Contacts, History, and Voicemail. And finally, clicking your picture will bring to the call forward settings.

Here are some other features worth to mention:

Federated calling
It allows you to call people in other companies on their Teams client from the contact history.

Calls escalation
It allows to add more participants to your one-to-one call.

Do-not-disturb breakthrough
Breakthrough capabilities allow you configuring certain people to have priority access, so they could bypass Do not disturb status limitations.

Delegation, also known as boss/admin or call-on-behalf allows your teammates to receive or make calls on your behalf (when you’re out for vacation or for any other reason). You can set up one delegate for multiple bosses, multiple delegates for one boss, or any combination of these options. Delegation allows to configure calls to simultaneously ring the delegates, or ring them after delay.

It allows you to do a blind transfer (without informing the person you plan to transfer it to), or to do a consult transfer (checking in with a person before transferring a call to them via chat or audio call).

The voicemails are delivered to the Exchange mailbox of the user with a transcript created for the voicemail. You can optionally enable profanity masking for the transcript, or, disable transcript at all. Exchange will be used for a deposit, compliance, and archiving of voicemails.
Generally, the voicemails can be played from Outlook or Teams but, please note that when you’re using Exchange server, then the voicemails won’t be displayed in the Teams client, and users will have to go to Outlook to see them (you should have at least Exchange server 2013 CU12 or higher).

Call Queues and Auto-Attendant
This enables companies to automatically route calls to specific departments, teams, or people in the organization. You can configure the time when the call queue should be available, as well as music on hold and custom messaging.

Service numbers
These are used for the scenarios that require high concurrency of simultaneous calls (potentially, hundreds of concurrent calls). Among these scenarios in Phone System are auto attendant, call queues, and audio conferencing.

Service numbers are always hosted by Microsoft, and you can get a new service number or port in your own number. These numbers can be toll or toll-free (the latter option means that communications credits are used to charge you for Audio Conferencing and Calling Plan minutes).

Admins’ bonuses


Administration portal is mostly used to configure individual settings or small groups of users. If you want to enable a large group of users or automate tasks such as user provisioning, you are also offered the full PowerShell access to script user enablement and configurations.


A rich set of reports will help you understand if the service is used and what the quality is. Usage statistics can be found in the usage reports per workload. There are separate reports on PSTN calling, showing how many users did how many calls in a certain time period.

In terms of call quality, you’re offered two tools:

Call Quality Dashboard, which provides an accumulated view on quality data. You can slice and dice the data by your needs, for example, by network segment, audio device, location, etc. Usually, you should in a proactive manner use Call Quality Dashboard and run a number of reports to find out if the call quality is what it should be. The picture below shows the Call Quality Dashboard example, where you can see the overall call quality, a graph with call quality per month showing in different colors, if a call was good or poor, and poor call percentage.

Call Analytics for individual calls is a more reactive tool, used when you get complaints on a bad experience, so that you can investigate that specific call, and find out the reasons. There are also the Call Detail records which give you information on who called whom and how long was that call.

Closing remarks

Remaining an important workload, voice has evolved to encompass the needs of a contemporary user. Teams offers all the voice capabilities and makes it easy to take full control of how you want to communicate.

Phone System covers both PBX, connecting calls between users, and PSTN features, allowing to reach external users on the PSTN phone network. For the latter you may use Calling Plans (completely cloud-based first-hand offer from Microsoft removing the requirement of having any physical servers on premises), Direct Routing (which involves your existing infrastructure and certified session border controller) or both.

Discover, how you can enhance collaboration in your company with voice capabilities from Teams.

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