Softphone Guide: Choose and Deploy a Softphone with Microsoft Teams or a PBX Such as 3CX

The short version: A softphone is an app that makes and receives phone calls over the internet on a PC or mobile device instead of a desk phone. If your company already runs Microsoft 365, the Teams client is a softphone once users have a Teams Phone licence and a phone number from a PSTN provider. If you run a separate PBX such as 3CX, its own client apps do the same job; confirm the vendor details in its documentation. Choose on the phone system behind the app, then fix headsets and the network, because those cause most call-quality complaints.

This guide is for IT managers and office managers in small and mid-sized companies who are replacing desk phones or adding remote staff. After reading it you will have a short list of selection criteria, a deployment sequence for the Teams route, a vendor-neutral checklist for a PBX route such as 3CX (vendor specifics to be confirmed in the vendor's own documentation), and a headset and network checklist.

What to check before you choose a softphone

A softphone is only the front end. The phone system, the number provider and your network decide how it behaves. Check these in order:

1. Which phone system is behind it. Teams Phone, a PBX such as 3CX, or a cloud phone provider. The app you use follows from this choice, not the other way round.
2. Which devices must be covered. Windows and Mac PCs, iOS and Android phones, and any desk phones you want to keep. Teams Phone works in all desktop and mobile Teams clients and on certified third-party devices (Microsoft Learn, 28 October 2026).
3. Where the phone numbers come from. The softphone does not provide numbers. A Teams Phone licence is separate from the PSTN service that supplies numbers and external calling.
4. Features your staff use every day. Voicemail, call transfer, call forwarding, call queues, an automated menu, and transfer between devices.
5. How it is managed. Who assigns users, who resets a user, and how you see call quality.
6. Emergency calling. How emergency locations are set for users who work from home or travel.
7. Support split. Who you call when a call fails: the phone system vendor, the number provider, or your IT provider.

Option 1: Teams as your softphone

The Teams client already runs on most Microsoft 365 PCs and phones. To turn it into a business softphone you need three things: a Teams Phone licence per user, a PSTN connectivity option, and phone numbers assigned to users.

What you need to buy or arrange

1. Teams Phone licensing. Anyone who needs their own phone number must be assigned a licence that includes Microsoft Teams and the Microsoft 365 Phone System application. Microsoft lists several valid combinations on its Teams Phone licensing page, including a stand-alone Teams Phone Standard licence added to an eligible base licence. Check the combinations that apply to your plan on that page (checked against Microsoft Learn, 28 October 2026). Prices are on Microsoft's official voice and calling pricing page, not here.
2. A PSTN connectivity option, one of Calling Plans (Microsoft is the carrier), Operator Connect (a certified operator), Teams Phone Mobile (a certified mobile operator) or Direct Routing (your own carrier through a certified session border controller).
3. Hong Kong and Singapore. Microsoft's Calling Plans page lists both Hong Kong SAR and Singapore among the billing locations for the Domestic Calling Plan outside the US, UK and Canada. Availability by country is published separately on Microsoft's "Country and region availability for Audio Conferencing and Calling Plans" page, linked from the Calling Plans page. A billing-location listing does not by itself prove Calling Plans work for a user in that country, so check that page for the country each user is licensed in before you commit.

Deployment steps

1. In the Microsoft 365 admin center, go to Billing > Your products > Add more products > Add-ons, and buy the Teams Phone add-on, then the Calling Plan if you chose that route.
2. Assign the licence to each user in the Microsoft 365 admin center under Active users.
3. Choose and connect the PSTN option, then get or port phone numbers.
4. Voice-enable each user. In the Teams admin center, go to Users > Manage users, open the user, and on the Account tab under Assigned phone number turn Enterprise Voice to On. The PowerShell route sets -EnterpriseVoiceEnabled $true through Set-CsPhoneNumberAssignment.
5. Assign the phone number to the user.
6. Set up emergency locations. How this works depends on the PSTN option, so follow the Microsoft guidance for the option you chose.
7. Set up voicemail, caller ID and call forwarding policies, then auto attendants and call queues if the company needs a main number.
8. Roll out in a pilot group first, then the rest.

Steps 1 to 8 follow Microsoft's Teams Phone setup roadmap (checked against Microsoft Learn, 28 October 2026).

Option 2: A PBX such as 3CX as your softphone (checklist)

With a PBX, the softphone is the client app that registers to your PBX. Product details differ between vendors and change between versions, so this guide does not restate 3CX editions, licensing or client app specifications. Read them on 3CX's own pricing and documentation pages for the version you plan to run.

What stays the same for any PBX softphone, and what to confirm in the vendor documentation:

1. Decide where the PBX runs: on your own server or virtual machine, or hosted by the vendor or a partner. This sets who patches it and who owns uptime.
2. Confirm the client apps for each operating system your staff use, and whether a browser client exists.
3. Confirm the licensing unit (for example by user, by extension or by simultaneous call) and the number you need at peak.
4. Get a SIP trunk or number provider and port numbers if you are moving from an old system.
5. Open the firewall for exactly the signalling and media ports the vendor lists. Do not open wide ranges from memory.
6. Install a valid TLS certificate on the PBX address so apps connect securely.
7. Provision users, then let each user install the app and sign in with the provisioning link or code the PBX gives them.
8. Test inbound and outbound calls, transfer, voicemail and calling from a mobile network, not only from the office.

If you want users to keep Teams for chat and meetings but use a PBX for calls, Microsoft documents Direct Routing for that: Teams connects to your telephony through a Microsoft-certified session border controller. Ask the PBX vendor how its Teams integration is supported.

Headset requirements

1. Use a headset with a microphone, not laptop speakers, for daily calls. Echo and room noise are the usual complaints on open-plan floors.
2. For Teams, choose devices that are Certified for Microsoft Teams. Microsoft says certified devices work as plug and play, with call control for answer, hang up, mute and volume (Microsoft Learn, 28 October 2026). The certified lists are on Microsoft Learn and in the Teams store.
3. In open offices, look for the Premium Microphone for Open Office designation, which Microsoft describes as picking up the headset user's voice without their neighbours'.
4. Bluetooth: native Bluetooth headsets are supported on Windows PCs, but Microsoft notes some users still need the USB dongle in crowded radio environments.
5. For PBX softphones, check that the vendor's app supports the headset buttons you rely on.

Network requirements

Check these before go-live, using Microsoft's Teams network guidance (checked against Microsoft Learn, 28 October 2026):

1. Bandwidth for audio. Microsoft lists audio in a one-to-one call at a minimum of 10 kbps each way, recommended 58 kbps each way and 76 kbps for best performance, per endpoint. Video and screen sharing use much more.
2. Do not route calls through a full-tunnel VPN. Microsoft recommends a split tunnel so Teams traffic goes straight to Microsoft 365, and notes some VPNs do not support UDP, which Teams needs.
3. Wi-Fi: use Quality of Service or Wi-Fi Multimedia, plan access point placement, and prefer 5 GHz for real-time media where devices support it.
4. QoS markings: Microsoft's recommended audio client source ports are 50,000 to 50,019 with DSCP value 46 (Expedited Forwarding). If you manage QoS, use these values as a starting point; a small business may not need QoS but should add it if it sees delays, and should not copy ports and DSCP settings blindly.
5. Firewall and NAT: do not alter UDP NAT mappings mid-session, and keep enough public addresses in the NAT pool.
6. WebSocket traffic should be allowed.

Common mistakes

1. Buying softphone licences before choosing the number provider. Teams Phone licensing and PSTN service are separate purchases.
2. Forgetting to voice-enable users. A licence alone does not turn on Enterprise Voice.
3. Leaving users on laptop speakers. Fix with a certified headset in every kit.
4. Testing only inside the office. Most problems show up on home broadband, hotel Wi-Fi and mobile data.
5. Sending voice through the full-tunnel VPN. This adds delay and may block UDP.
6. Skipping emergency location setup for remote staff.
7. Opening firewall ranges from a forum post instead of the vendor's current list.

How to check it worked

1. Place calls both ways: to an external mobile and from it, then to a colleague.
2. Test transfer, hold, voicemail and forwarding from each device type.
3. Test from a home network and from mobile data.
4. Review call quality for the pilot group after a week using the Teams admin center call analytics or the PBX's own reports.
5. Confirm the main number and menu route correctly and that emergency location data is set for each user.

FAQ

What is a softphone?

A softphone is software that lets you make and receive telephone calls over the internet using a computer, tablet or smartphone instead of a dedicated desk phone.

Is MS Teams a softphone?

Teams is a collaboration app with calling built in. With a Teams Phone licence and a PSTN connection it can place and receive external calls, which makes the Teams client act as a softphone.

What is the best softphone?

There is no single best one. The best softphone is the client of the phone system you have chosen, used with certified headsets and a network that has been tested. Use the selection checks above.

Can you give me an example of a softphone?

The Teams client with Teams Phone, and the client apps of PBX products such as 3CX, are examples. Both register users to a phone system rather than to individual phone numbers.

Is there a softphone for Windows?

Yes. Teams Phone works in desktop clients on PC and Mac and in mobile clients, according to Microsoft Learn. PBX vendors publish their own Windows apps; confirm the supported versions in their documentation.

Where to go next

To have a provider run the softphone rollout, headsets and network checks included, see our telephony service, or look at mobile device management for phones, Microsoft Teams solutions and network hardware maintenance for the parts around it.

Sources checked 28 October 2026: Microsoft Learn pages on Teams Phone, Teams Phone licensing, PSTN connectivity, Calling Plans, Direct Routing, Teams network preparation, Teams QoS and certified devices. 3CX product details are not restated here.