Microsoft on-premises server product that runs Office Online.
Hi @Audrie Poll
Thank you for posting question to Microsoft Q&A Forum.
According to this issue, please check on your email via the webmil version to see if you could sign-in via your IMAP account. You might need to contact your email service provider to ask for your sign-in information - if you are using Outlook as email client and you have issue with IMAP, please remove the account and sign-in again after clarifying back with your email service provider.
As Stefan mentioned above, IMAP account is not related to Microsoft as we use Microsoft Exchange for synchronization.
Please let me know once you have new update from your end.
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