Microsoft will be removing the ability to use basic authentication in Exchange Online from 1st October 2022. This affects Exchange ActiveSync (EAS), POP, IMAP, Remote PowerShell, Exchange Web Services (EWS), Offline Address Book (OAB), Outlook for Windows, and Mac. SMTP AUTH will also be disabled in all tenants in which it's not being used. This decision requires customers to move from apps that use basic authentication to apps that use Modern authentication. The reason behind this change is to increase security and subsequently further protect your data. You can learn more about this via Microsoft's article on the matter  

With regards to Halo, this change impacts those using POP3, EWS and IMAP connections for exchange online and Microsoft services. We recommend reconfiguring your mail as Azure, which you can learn how to do here.

NB: This only applies to customers using Office365 for their Emails. If a customer is not using Office365 for their emails, they can still use the basic authentication (POP, IMAP etc..) methods for mailbox connection.