In a recent support case the Skype for Business Mac client wasn’t connecting to Exchange Web Services (EWS) after the EWS Access Policy was configured with the following cmdlets:
Set-CASMailbox -Identity brick@borderlands.lab -EwsApplicationAccessPolicy EnforceAllowList -EwsAllowOutlook $true -EwsAllowMacOutlook $true
Set-CASMailbox -Identity brick@borderlands.lab -EwsAllowList @{add=’UCWA/*’, ‘OC/*’, ‘OWA/*’}
https://docs.microsoft.com/powershell/module/exchange/client-access/Set-CASMailbox
Get-CASMailbox -Identity brick@borderlands.lab | fl Name,EwsApplicationAccessPolicy,EwsAllowOutlook,EwsAllowMacOutlook,EwsAllowList
EWS was working except on Skype for Business Mac, after reviewing the logs the issue was that SfB Mac user agent is SfBForMac.
To fix this we simply add SfBForMac to the EwsAllowList with:
Set-CASMailbox -Identity brick@borderlands.lab -EwsAllowList @{add=’SfBForMac/*’}
Please note that the previous example was only for a test user, we can also configure it on the Organization Level:
Set-OrganizationConfig -EwsApplicationAccessPolicy EnforceAllowList -EwsAllowOutlook $true -EwsAllowMacOutlook $true -EwsAllowList @{add=’SfBForMac/*’,’UCWA/*’, ‘OC/*’, ‘OWA/*’}
https://docs.microsoft.com/powershell/module/exchange/organization/Set-OrganizationConfig
Get-OrganizationConfig |fl Name,EwsApplicationAccessPolicy,EwsAllowOutlook,EwsAllowMacOutlook,EwsAllowList
UC Lobby 
Hi, My company is moving to Microsoft Teams and we are a Polycom House with models VVX 411 to VVX 500 model VOIP phones. Can the Lync client bridge the two together so our users can make calls through thier polycoms in Teams? Can they also do video conferencing from their screens using these phones?
I think the best option in this case is to ask Polycom about this.
FAQ – Polycom Phones and Microsoft Teams
https://www.polycom.com/content/dam/polycom/common/documents/faqs/polycom-phones-and-microsoft-teams-faq-enus.pdf