Every message you send to a coworker via Office Chat have indicators that acknowledge the delivery of a message. Here is what they mean:

•  – Private message or Team message successfully delivered to the Office Chat server.
•  – Private message successfully delivered to the phone / Windows Desktop / Mac of the recipient. Please note: This does not indicate that the message was read, just that it was delivered.

Also note that in a team you will only see one check mark indicating that the message was successfully delivered to the Office Chat server.

If you only see a single check mark next to your message, there is likely nothing wrong with Office Chat or your phone. There may be several reasons why your message is delivered to the server, but not to the recipient yet.

• The message was in a team chat so only one check mark indicator is applicable.
• Their phone might be turned off or their phone’s battery might be dead.
• They may not be connected to the internet (for example, if they are in an elevator, roaming, or have no data credits).
• They might have seen the notification on the screen, but did not launch the app to acknowledge message receipt (very common in case of iPhone recipients).
• They could be sleeping, especially if they live in a different time zone.