When updaiting Mailspring to version 1.12 you may be unable to receive new e-mails after the upgrade, see a "Password Management Error" or the error "Your Mailspring ID is missing required fields". If this is the case, please follow these steps to resolve it:

1. Snap only: If you have installed Mailspring via the snap package, ensure that Mailspring is able to access your operation system's key storage to encrypt your e-mail account credentials. To do so, run sudo snap connect mailspring:password-manager-service in a terminal.
2. Log out of your Mailspring ID in the preferences.
3. Follow the steps noted here regarding your operating system and setup: https://community.getmailspring.com/t/password-management-error/199
4. Log in again into your Mailspring ID in the preferences.
5. In the account preferences, reconnect all your e-mail accounts.

If these steps are unsuccessful, completely uninstall Mailspring so that its configuration gets removed. Then freshly install the latest version. This should resolve all migration issues. However, you will lose all settings and configurations that you made within the old Mailspring versions.

In the case of issues, please use this help thread: https://community.getmailspring.com/t/password-management-error-after-the-latest-upgrade/7298