Observed behaviour:
the iOS Mail app is not performing the scheduled fetch for favourite mailboxes of accounts (like Gmail, Yahoo, IMAP third party) which do not support Push. Notifications for such new mails are also not generated. Scheduled fetch and notifications do not occur with any of the fetch frequencies (every 15 minutes, every 30 minutes, hourly, Automatic) on favourite mailboxes even after a lapse of many hours/ multiple consecutive fetch cycles.
Upon opening the Mail app, the respective favourite mailboxes show unread count displayed against each. Yet they don’t show notifications for those mails. The notifications occurs for Favourite mailboxes only if its mail account supports Push, or it is manually opened.
Expected behaviour:
The native iOS Mail app should perform scheduled fetch and notifications on favourite mailboxes in every fetch cycle for all IMAP/ Gmail/ Yahoo mail accounts even if they do not support Push. The scheduled fetch should should work on any of the available frequency options (Automatic/ hourly/ Every 30 minutes/ Every 15 minutes).
All the favourite mailboxes should get fetched at least once in every fetch cycle as per schedule and no such mailbox to be missed and left out from any scheduled fetch - e.g. if the fetch frequency is ‘Every 15 minutes’, then every favourite mailbox should get fetched once every 15 minutes. A notification should get generated for every new mail received on scheduled fetch in each favourite mailbox.