How can I know if anyone has read my message?

In Messenger, you can know message reading status in real time. The steps are as follows:

•Hover over the message you sent, and a green circle icon will appear.

•You can see who read the message through the green circle. The circle is gray when no one has read it; it is partially green when some of the group members have read it; and it will become a green circle with a check mark when everyone has read it.

•Click on the circle icon to view who has read and who hasn't.

•If you @-mention colleagues, there will be a small gray dot in the upper right corner of their names. When they read the message, the small gray dot will turn green.

How can I check if my messages have been sent successfully?

If you see a red exclamation mark after sending a message, it means that the message failed to be sent. If a gray circle appeared on the right of your message, it represents the message has been sent successfully but just hasn't been read yet.