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Mail Not Syncing After Mac Sleep — Troubleshooting Guide

Overview


If your Mac is left in sleep mode for an extended period (overnight, weekends, or several hours during the day), Airmail may fail to download new messages that arrived while the Mac was asleep, or not catch up to the latest state of the mailbox after wake. This is most commonly reported on shared Exchange / Microsoft 365 accounts and on recent macOS releases.


This guide collects the system-level and application-level checks that resolve the majority of post-wake sync issues.


Symptoms


  • Messages received during sleep do not appear in Airmail after wake, although they are visible in the Web interface or on other devices (iPhone, iPad).
  • Resetting the message cache temporarily restores synchronisation, but the issue returns on the next sleep cycle.
  • The behaviour is more frequent on shared Exchange folders.


macOS System Settings to Verify


  1. Wake for network access

System Settings > Battery > Options — enable "Wake for network access". This is a Mac-wide setting (it does not have a per-app toggle) and is required so that the Mac can refresh data while the lid is closed or the display is off.


  1. Login Items & Extensions — Allow in the Background

System Settings > General > Login Items & Extensions > Allow in the Background — confirm that Airmail is listed and toggled ON. If Airmail is not listed, please launch the app once and approve any permission prompts that appear.


  1. Notifications

System Settings > Notifications > Airmail — ensure notifications are enabled and that background activity for the app is allowed.


  1. Privacy & Security — Full Disk Access

System Settings > Privacy & Security > Full Disk Access — add Airmail to this list. Full Disk Access can affect the application's ability to access locally cached Exchange data.


If Airmail does not appear in any of the above panels, this is itself diagnostic information — it usually means the system has not yet prompted the app for the relevant permissions, or that the registration has not completed correctly. In this case, please:


  • Fully quit Airmail (right-click the Dock icon > Quit).
  • Restart your Mac.
  • Reopen Airmail and approve any permission prompts that appear.
  • Recheck the panels listed above.


Airmail Settings to Verify


  1. Refresh Interval

Airmail > Settings > Accounts > [your account] — review the refresh interval. A shorter interval can help Airmail catch up faster after the Mac wakes.


  1. Account authentication

Make sure the affected account does not show any error icon. For Exchange / Microsoft 365 accounts, please ensure that the account is signed in via OAuth (Microsoft sign-in option) rather than via manual IMAP, when possible.


  1. Quick Cache Rebuild Shortcut

Hold the Option key while opening Airmail. The diagnostic dialog will offer the option to Reset / Rebuild the database directly at launch. Note: the Option key must be held immediately before launching Airmail and kept pressed until the application window fully opens.


When to Reinstall


If the issue persists after the steps above and Airmail still does not appear in the system permission panels, a clean reinstall can re-register the application's background services. Please refer to our dedicated guide:


Uninstall and Install Airmail — Airmail for macOS


Before reinstalling, take note of any custom rules, signatures, and aliases configured under Preferences > Accounts, so they can be reapplied afterwards. Airmail does not currently provide a built-in export/import tool for account settings, but server settings are auto-discovered for most major providers (iCloud, Gmail, Outlook/Microsoft 365), and only the Exchange server address, username, and password are typically required for shared Exchange accounts.


Reporting the Issue to Support


If the issue persists after a clean reinstall, please contact our support team and include:


  • The exact Airmail version (Airmail > About Airmail).
  • The macOS version.
  • The mail provider used by the affected account (Gmail, iCloud, Exchange, Microsoft 365, generic IMAP).
  • Whether the issue affects only one account or multiple accounts.
  • Approximately how long the Mac is typically asleep before the issue occurs.
  • The approximate time of one or two recent occurrences.


This information allows our technical team to correlate the report with our internal investigation and helps us reproduce the behaviour.


Updated on: 05/08/2026

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