Apple Mail not receiving emails after macOS update?

If Apple Mail is not receiving emails after a macOS update, it usually happens due to compatibility issues between the updated system and existing mail settings. The update may reset IMAP/SMTP server details, cause mailbox indexing errors, or conflict with outdated account configurations. In some cases, syncing pauses because iCloud storage is full or Mail rules behave unexpectedly after the update. Rechecking account settings, rebuilding the mailbox, and installing any pending patches usually fixes the issue. To stay safe during such disruptions, keeping a backup of emails with the SysInfo iCloud Backup Tool ensures your data remains accessible if syncing fails.