We get a lot of questions about “broken” follow up – there is only one follow up option – a basic flag – and reminders aren’t available for it.
Follow up is not broken, its just not supported for IMAP accounts. You’ll have the full range of follow up flags and can set reminders if you move the items to a local pst.
All other account types (POP3, Outlook Connector, and Exchange) support the full range of follow up flags and reminders.