HTC One M8 User Manual page 271

4. Enter the email address and password for your email account, and
then tap Next.
Some email accounts allow you to set the sync schedule. By
default, HTC One uses Smart Sync to save battery power. See
What is Smart Sync?
5. Enter a name for your email account, and then tap Finish setup.
What is Smart Sync?
Smart Sync automatically extends the sync time the longer the Mail app is
inactive. Set your email account to Smart Sync when you don't need to
check new email messages frequently. Smart Sync helps save battery
power.
If you want to receive email messages as they arrive, select another Peak
time sync and Off-peak sync schedule in the email account's Sync, Send &
Receive settings.
on page 271.
Email 271