HTC One M8 User Manual page 237

Backing up text messages by email
You need to set up your email account in the Mail app.
1. Open the Messages app.
2. Tap > Back up/Restore SMS.
3. Tap Back up > Back up SMS via mail.
4. 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.
5. Enter your email address.
6. Compose your email message, and then send it.
Restoring text messages
1. Open the Messages app.
2. Tap > Back up/Restore SMS > Restore.
3. Choose how you want to restore the messages, and tap Next.
4. Tap the backup to import.
5. Enter the password you've set for this backup. If you didn't set a
password, select This backup file is not password protected.
Sync, backup, and reset 237