E-mail downtime during conversion of Azure domain from federated to managed?, will client connectivity be effected during this transition?

Hello Experts. Will there be downtime for E-mail when converting a domain in Azure from federated domain to manged domain using Pass-through sync, with Modern auth enabled? We have ADFS 3.0, with centralized mailflow. and I would like to start converting some of the domains in Azure to managed. I know its just a few powershell commands to get this done, but how long does this transition take?, and will the users Outlook client still be able to connect to Exchange Online, will OWA still work during this transition. Please let me know and thanks in advance.
Newguy 123Asked:
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Vasil Michev (MVP)Commented:
Depends on what you understand by downtime. There might be some downtime for users trying to login to their mailboxes depending on how fast you perform the conversion, but the actual mail flow will not be interrupted. If you have managed AD FS via AAD Connect, you can use the AAD Connect setup wizard to run the conversion, and it will generally be easier/faster. Otherwise, you have to manually convert the domain, convert all users, configure PTA. Optionally you might also configure and run password sync at least once, so that the on-prem passwords are synced to Office 365, but in general with PTA you should need to use the cloud password anymore.

If you schedule it outside of working hours or over the weekend, nobody will probably notice a thing, apart from being prompted for credentials once they get back in the office.
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