I'm trying to setup another account in Outlook, besides my primary, (this is another account through Account Settings > Email > New, not a shared mailbox) and I cannot get it to work. I can add the account just fine (autodiscover works and I get all the green checks) but when I try to open it I get an error "The set of folders cannot be opened. The file is not an Outlook data file (.ost)". If I remove the account and add it back again with cached mode disabled I get the error "The set of folders cannot be opened. Network problems are preventing connection to Microsoft Exchange" I'm using the C2R version of Outlook but I've tried it with the MSI version and it's the same thing. Both accounts are Exchange Online accounts. Is this supported? Are other people able to add multiple EXO accounts to a single Outlook profile?
It works for me: adding two different Exchange Online mailboxes in the profile. Both of them work as expected.
Please ensure the second mailbox is working when setting up it in a single profile.