Microsoft have annouced they will be restricting access to Microsoft Teams data via EWS from the 30th September see https://devblogs.microsoft.com/microsoft365dev/restricted-access-to-microsoft-teams-data-via-ews-starts-september-30-2022/ . If you are using EWS to access any teams data you will need to move to the Graph API's https://docs.microsoft.com/en-us/microsoftteams/export-teams-content one thing to note is "Microsoft Teams APIs in Microsoft Graph that access sensitive data are considered protected APIs" so there are some extra steps and time you need to access this data and be aware of the potential need to pay for that access eg "On July 5th 2022, metered consumption is active, and will be billed through an Azure subscription" ref https://practical365.com/teams-export-graph-apis/.
As well as EWS and Remote PowerShell (RPS) other mail protocols POP3, IMAP and SMTP have had OAuth authentication enabled in Exchange Online (Official announcement here ). A while ago I created this script that used Opportunistic TLS to perform a Telnet style test against a SMTP server using SMTP AUTH. Now that oAuth authentication has been enabled in office365 I've updated this script to be able to use oAuth instead of SMTP Auth to test against Office365. I've also included a function to actually send a Message. Token Acquisition To Send a Mail using oAuth you first need to get an Access token from Azure AD there are plenty of ways of doing this in PowerShell. You could use a library like MSAL or ADAL (just google your favoured method) or use a library less approach which I've included with this script . Whatever way you do this you need to make sure that your application registration https://docs.microsoft.com/en-us/azure/active-directory/develop/quickstart-register-