How far back do you want to synchronize e-mails in iPhone? [PRO] If you don’t think you need to access all your e-mails from your mobile, we recommend that you perform these settings. The fewer days, the more you can save on your battery consumption. This requires Work2Go Pro If you don’t have Pro today, you can upgrade by contacting our support. Go to Settings > Mail, Contacts, Calendars > Select the account. Now you see the account’s general settings. Click Mail days to sync to choose how long you want to sync e-mails to your mobile.