When Microsoft Teams messages fail to send — sitting there with a warning icon, showing as stuck, or simply never appearing on the other person’s screen — it can be difficult to know whether the problem is on your end, the recipient’s end, or with Microsoft’s servers. Message delivery failures in Teams are usually caused by a network or connectivity issue, a problem with the Teams service itself, or corrupted local data. This guide walks through the most effective fixes for both classic and new Teams.
Check Microsoft’s Service Status
Before spending time troubleshooting your own setup, check whether the Teams messaging service is experiencing an outage. Visit status.office365.com and look for any active incidents under Microsoft Teams. If there is a service disruption, you will need to wait for Microsoft to resolve it — no local fix will help.
Check Your Internet Connection
Teams requires a stable connection to send and receive messages. Run a quick check: open a browser and try loading a website. If browsing is slow or failing, resolve your network issue first. Try switching from Wi-Fi to a wired connection, restarting your router, or temporarily disabling a VPN to see whether that is interfering.
Check Teams’ Connection Status
In classic Teams, look at the bottom-left corner of the app. A yellow or red status indicator means Teams has lost its connection to Microsoft’s servers. Hovering over it will show the current connection state. Clicking Try again or signing out and back in usually restores connectivity.
In new Teams, a connection warning banner typically appears at the top of the screen when connectivity has been lost.
Sign Out and Sign Back In
Authentication token expiry can cause messages to fail silently. Click your profile picture in Teams, choose Sign out, close Teams fully via the system tray, reopen it, and sign back in. This is particularly effective when messages were sending fine earlier in the day but have since stopped.
Clear the Teams Cache
Corrupted local data is a reliable cause of messages failing to deliver or being stuck in a sending state. Clearing the cache forces Teams to re-sync its data from Microsoft’s servers.
The full process for both classic and new Teams, on Windows and Mac, is covered in the guide on how to clear the Microsoft Teams cache. After clearing the cache, restart Teams and sign in again before testing.
Check Whether the Recipient Is in the Same Organisation
Messaging external contacts (guests or federated users from other organisations) has different routing than internal messages. If messages are only failing to send to a specific external contact, ask your IT team to verify that external access and federation settings are correctly configured in the Teams admin centre under Users > External access.
Check the Message Size and Content
Teams has a message character limit of approximately 28,000 characters. Very long messages may fail without a clear error. If you are pasting a large block of text, try splitting it into multiple shorter messages. Similarly, some organisations restrict certain file types and links — if a message contains an attachment or URL that is blocked by your organisation’s policies, it may fail silently.
Try a Different Chat or Channel
To narrow down whether the problem is with a specific conversation or affects Teams globally on your device, try sending a message in a different chat or channel. If messages send fine elsewhere, the original conversation’s data may be corrupted. Try leaving and rejoining the channel, or asking the other party to start a new chat thread.
Disable Firewall or Proxy Temporarily
Corporate firewalls and proxy servers can interfere with Teams’ messaging protocols. If you are on a managed corporate network, ask your IT team to verify that the required Microsoft 365 endpoints are whitelisted. Microsoft publishes the full list of URLs and IP ranges required for Teams at learn.microsoft.com/en-gb/microsoft-365/enterprise/urls-and-ip-address-ranges.
Reinstall Teams
If all other steps have failed, a clean reinstall is the most thorough reset available. Uninstall Teams, delete the residual app data folders (as described in the cache clearing guide), then download and install the latest version from the Microsoft Teams download page.
Related Issues
If Teams is loading slowly in addition to message failures, see Microsoft Teams running slow or not loading. If you are not receiving message notifications, the fix may lie in Microsoft Teams notifications not working. For call problems that appear alongside messaging issues, see Microsoft Teams calls keep dropping.
For a full index of every Teams guide and troubleshooting fix on Serverman, see the Microsoft Teams complete guide and troubleshooting hub.
