
Hi @Alena ,
External users need to enter a verification code when accessing for the first time, and only need to enter the account password of the external mailbox for subsequent access. Although it shows that you need to log in with the M365 account, when you log in with an external account, the system will automatically create a virtual Microsoft account for the external account for external users to use, so you can log in with the external account and password normally.
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