Imo allows users to check the sent/read status
of your message/file/media in the private chat
via symbols as below:
1 check "√": Not reach (network problem)
or you are blocked;
Double checks "√√": Received;
Round circle "o": read by the other side.
Red sign "! ": Network problem.
Notice:
1. When you are blocked by him, all you sent
will show 1 check "√".
2. When he sets Read Receipts (in Profile page
- Settings - Privacy) as "Nobody", it will not
show round circle "o" even if your messages
are read by him.