When the PBX is enabled for remote access and it is understood how to create SIP credentials for users, the connector service needs to be configured to connect to the PBX.

This requires two areas of configuration:

  • A Service-level configuration to define how every user connects to the PBX
  • Per-user configuration to allow each user to provide a device registration to the PBX


Configure the connection to your PBX

In the connector portal, the Services tab allows for the overall configuration between Teams and the PBX.

When selecting the PBX option, there will be a list of available PBX types or services. Select the most appropriate template for your PBX, if the PBX is not listed, select ‘Custom’ or ‘Not listed’. This will bring up the all available options for the PBX connection. If you’ve selected a defined PBX template, then a subset of these fields will be available in the configuration form.


How to complete the PBX configuration form

The following field descriptions will assist you in configuring the PBX settings form

Country & State/Province

The connector service has servers spread globally across multiple continents. Enter the location of PBX here to ensure the most appropriate service location is configured as the primary note for the PBX to connect to. This ensures best call quality. The service will configure two nodes for each PBX to ensure high availability.

SIP Domain

This is usually just the IP address or public host name used to reach the PBX. If your PBX requires you to use a specific value here, then do so and specify the IP address or public host name in the SIP Proxy field. Do not enter a port number on the SIP Domain

SIP Proxy

This is usually left blank but can be used to specify the IP address or public host name to reach the PBX if the PBX requires the SIP domain to be set to a different value.

If you need to specify a different port for registration to your pbx (default is 5060), aA port number can be specified by additionally setting a proxy address and appending a colon and the number to the SIP Proxy field. e.g. myhostname.com:5056

Authentication Type

This should be set to ‘Registration’ unless you are deploying an advanced configuration and have been advised otherwise.


‘UDP’ is the most common protocol to use, and the one most likely to be supported particularly on older PBXs. However, if the network equipment does not handle fragmented UDP packets then ‘TCP’ could be used.

If end to end encryption is required, then select ‘TLS’.

Encryption Media

This should be set to ‘no’ unless encryption is required, and the ‘TLS’ protocol is configured.

Supports Refer 

In most cases this can be set to ‘Yes’. Only if the PBX does not have support for transferring calls should this be set to ‘No’.

Suppress Contact Data Param

If you have a single-organization PBX using a single public IP address, then you should set this to ‘No’ as the alternative can hinder correct function with some PBXs.

If you have a multi-tenant or multi-server PBXs then try setting this to ‘Yes’ and if it causes an issue, then revert to ‘No’.

Outside line prefix

If the PBX required a number to be dialed to reach an outside line, enter this here and it will be automatically prepended; this means Teams users do not need to specify this when dialing and can simply dial the destination PSTN number.

E164 Number Format

Teams uses E164 numbering, which is where numbers begin with a ‘+’ followed by the country code.

If the PBX expects localized numbers, then you can specify the mapping here.

e.g. if the PBX expects in-country numbers to start with a ‘0’ and international numbers to start with ‘00’ followed by the country code then enter ‘0’ as the national dialing prefix and ‘00’ as the international prefix.
See the separate knowledgebase articles on E164 number management

Creating SIP accounts on your PBX

Typically SIP credentials will contain the following information. PBX systems often refer to SIP devices rather than users. This is because a user on a phone system may have several devices (e.g. Desk Phone and Soft Phone) that will be connected to their user extension:



SIP Username

A per-user or per-device identity. Occasionally the same as the extension number.

SIP Auth Username

Not always required; if SIP Username is the user identity then SIP Auth Username is the specific device identity, often more complex than SIP Username and not memorable.

If this field is not required, then it can be left blank

SIP Password

A per-device/user password setting 


The per-user settings are entered into the service ‘Users’ tab to map each Microsoft Teams user to the SIP device credentials created.

A phone number is also required, this may be a full DID number or just an extension. The number must be unique for each user. The country code for the user is driven from the User’s country setting in the Office 365 license area – if it is incorrect then alter it in the Office 365 portal and then run another sync process

SIP Username should not include an @ symbol.

Note: Remember to click Sync again once this user configuration is done, as this will perform the Office 365 configuration for those users.

Additional configuration topics

Dialing Limitations

There are some dialing rules built into Teams that cannot be circumvented:

  • Numbers beginning with ‘0’ are converted to full E164 numbers. If you have extension numbers beginning with ‘0’ then consider changing them so they don’t have this prefix

  • Many PBXs have feature codes beginning with ‘*’ that can be dialed. Most will work from Teams, but *11, *12 and *13 do not. Microsoft have indicated that they reserve the right to block some other two-digit star codes as they allocate them for new native Teams features, although at the time of writing there is no sign of this. If you make use of these blocked feature codes then look to see if the PBX can be configured to change the codes to ones that will not be blocked by Teams.


SIP Registration indicators and error messages

SIP registration status is shown against users in the Users tab. This indicator will show green if registration is operating normally.

If the indicator is Red, the brief reason will be displayed when you hover the mouse pointer over the indicator. The message shown varies between PBX vendors, and some of the more common ones are shown in the table below:




Unable to resolve URI

Either the SIP Proxy (if specified) or SIP Domain is incorrect

No response received after xx seconds

The PBX did not respond. Check the firewall and the SIP Proxy/Realm. Specify a port in the SIP Proxy if required.

Authentication Failure

Usually means that the SIP Username, SIP Auth Username (if specified) or SIP Password are incorrect.


It could be that the SIP domain or realm is incorrect if the PBX checks this.



Invalid password

Not found

Proxy Authentication Required


User unknown