You can either sync email or push email. - - - Method A. Sync email: 1. Configure poll frequency: "Settings" > "Accounts" section > tap the account you want to configure > "Fetching mail" > "Folder poll frequency" > choose the option you prefer. Please note that the minimum poll interval is 15 minutes. If 15 minutes is too long for you, you should use push email instead. 2. Select the folders to sync: Tap hamburger button (three horizontal bar) on the top left corner. If your email accounts are hidden, tap "Show accounts" at the bottom of the screen > tap the account you want to configure > "Manage folders" > tap the folder you want to configure > turn on "Enable sync" and turn off "Enable Push". - - - Method B. Push email: The following link might be helpful: Configure push email for Thunderbird for Android https://support.mozilla.org/en-US/kb/configure-push-email-thunderbird-android