Mailflag notification filter

Mailflag is a notification service for IMAP IDLE, offering four different modes of operation.
Foreground Service runs with a small icon in the notification area. If your device allows it to keep notifying when the screen is off, this is the preferred choice. If not, switch to Polling Mode 1, 5 or 15 minutes.
Partial Wake Lock (foreground service) keeps notifying while the screen is off, at the cost of increased power usage (typ. 25 mA).
Background Service runs without permanent icon, is less persistent (may stop when system resources get low).

Polling Mode flags all messages 'seen' to prevent repeated notification, and hence will notify on one device only.
Mail that arrives during connection loss will only be notified in Polling Mode.
You may need to check the Wi-Fi Sleep Policy of your device.
Under Android 6.0+ the app will ask once for exclusion from Battery Optimization ('Doze mode').

Configurable filters limit notifications to specific (groups of) sender addresses and/or subjects.
Each filter may contain multiple ||-separated strings. A string within slashes is evaluated as regular expression, for instance: /@gmail.com[>)]?$/
Notification sound, LED color, etc. are configurable using the Options menu.
The new email notification can launch any non-system app with a (package) name containing 'mail'.
The notification shows 'Mailflag:' in its title, which allows detection by e.g. Tasker (%NTITLE variable).

The current version supports a single connection using imaps (oauth/strict/any) for SSL, imap for NON-SSL.
Note: imaps (oauth) supports login to imap.gmail.com using a device Google account.
Backup/Restore allows easy switching between different accounts.

Mailflag will run with a trial limitation until a license is purchased (in-app purchase, $2.99). The application is fully functional, but the service stops after 72 hours. A 'Force stop' will reinitiate this period. The license removes this 72 hour limitation.
PLEASE RUN MAILFLAG IN TRIAL MODE FIRST, TO VERIFY THAT IT RUNS ON YOUR DEVICE AND MEETS YOUR EXPECTATIONS.