HTC One Remix - Manual (Page 138)

Delete a
conversation Press and hold a contact (or phone number), and then
tap Delete.
To delete multiple conversations, on the All messages
screen, tap > Delete threads, and then select the
conversations to delete.
In the Messages settings, tap General > Delete old messages to
auto delete old messages.
Preventing a message from being deleted
You can lock a message to prevent it from being deleted even if you delete
the other messages in the conversation.
1. On the Messages screen, tap a contact (or phone number) to
display the exchange of messages with that contact.
2. Tap the message that you want to lock.
3. Tap Lock message on the options menu. A lock icon is
displayed.
138 Messages