A client is connecting to three different Exchange Servers from within one Mail Profile within Outlook.
Is there a way to toggle a single account into Work Offline mode, or will clicking the Work Offline button affect all accounts?
Clicking the "Work Offline" button affects all accounts. This is the application-wide setting.
This is so frustrating. I had the same problem. Specifically that if one mailbox can't connect to, eg an IMAP server, it prevents you using all mailboxes because you can't turn off the constant prompts, and each prompt blocks the background synchronisations (both disk and network).
Warning!! This is risky, laborious, and should not be required. But after 8 days trying to migrate an offline IMAP account to a new server, it's the only method I know that works. This use case is specifically for migrating a mailbox to a new server if for some reason the existing server becomes unavailable.
To get the account online again, you need to create a new online account, then copy each folder back from the offline account to the new online account.