HTC One User Manual page 216

216 Sync, backup, and reset
5. Enter the password you've set for this backup, and then tap OK.
Backing up your text messages
Keep important text messages by backing them up to the phone storage.
You can easily restore backed up text messages after you've deleted them
from your message list.
1. Open the Messages app.
2. Tap > Back up/Restore SMS > Back up > Back up SMS.
3. To help protect your data, set a password for your backup. Be sure
to remember this password. You'll need to enter it again when
restoring messages.
If you don't need a password, select Do not password protect this
backup.
4. Enter a name for your backup file, and then tap OK.
Backing up text messages by email
You need to set up your email account in the Mail app.
1. On the Messages screen, tap
2. Tap Back up > Back up SMS via mail.
> Back up/Restore SMS.