Aqua Mail offers a variety of customization options for fine-tuning when and how often it checks for new messages, as well as whether to observe any data restrictions. This is all available in Settings > Mail, receiving.
The app allows for scheduled sync to occur at a defined interval (in minutes) as well as a specific time.
You may, for example, schedule your mail check at precisely 08:10:10 AM and every 30 minutes following by adjusting the mail check interval to 30 minutes, then configuring a time reference point of 08:10 AM, and lastly a settle in delay of 10 seconds.
Settle in delay is a useful tool for users running background optimization apps which limit network connectivity. Adding a few seconds of delay lets your network connect normally after the background optimizer has enabled Cellular or Wi-Fi connectivity on schedule.
Mail synchronization can also be event-triggered via the system's Auto-sync setting, device reboot or resume of the app.