Skype for Business uses a number of extensions to the SIP/SIMPLE instant-messaging protocol for some features. As with most instant-messaging platforms, non-Microsoft instant-messaging clients that have not implemented these publicly available extensions may not work correctly or have complete functionality. Skype for Business supports federated presence and IM to other popular instant message services such as AOL, Yahoo, MSN, and any service using the XMPP protocol, although support for XMPP has been deprecated in Skype for Business 2019. Text instant-messaging in a web browser is available via Skype for Business integration within Exchange Outlook Web App.
