With the IDLE function enabled, Mac Mail will make a continuous connection to the HG server, and this will contribute to the problem. Instead, you can configure Mac Mail to periodically check for new mail. A reliable frequency for the idle feature is every 10 minutes to ensure that Mac Mail is cleaning out any lingering processes.
To disable the IDLE feature:
- Select Mail | Preferences from the menu.
- Choose Accounts.
- Select the desired IMAP account.
- Go to the Advanced tab.
- Uncheck Use IDLE command if the server supports it.
- Additionally, you can uncheck Include when automatically checking for new mail.