Teams Diagnostic code 500/16825

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Teams Diagnostic Code 500/16825 error message when trying to contact external user from Teams. I need help please. diagnostic (2).png

11 Replies

Hello @ayenco  I found a couple of unverified articles you might want to read; let us know if they work for you.


How to fix Microsoft Teams error code 500 on Windows 11/10 (


FIX: Microsoft Teams Error Code 500 (Full Guide) (

Having the same problem and can't get my head around it. Any news on what could help?

"Es ist ein Problem beim Versenden Ihrer Nachricht auftgetreten. Geben Sie den Diagnosecode für den500/16825 Administrator an, damit dieser Ihnen bei der Problembehandlung helfen kann."


Some questions to try to help

1. Can you contact other users via federation - i.e. is this the only user you can't chat to

2. Can the other user talk to people other than you via federation?

Trying to narrow down where the issue might be. Tenant admins can block users from using federated chat or it might be another issue

If you want to share the contact details on DM I can see if I can federate to them or to you


1. Unfortunately its of all users in that federation. They are all Skype users. In my admin center we have activated the "Allow users in my organization to communicate with Skype users." option.

2. Yes similar to the screenshot above the external users can even contact me, but I cannot answer.

With other external users / service providers we don't have any issues. I will DM my contacts with you for federation check.

We narrowed the issue down to the remote end/SfBS end issue
We are having same/similar issue with a customer we are deploying Teams for. If you have any details to share, will be much appreciated.
Customer is moving from onprem sfb to Teams. Sometimes users trying to IM between onprem sfb and teams user, getting the same error/behavior
So far I haven't found the correct person on the sfb end to try different configurations.
Personally my assumption is that the users might not be fully migrated from sfb on prem to teams yet.
To be honest with sfb online breaking away now, I am not sure what the croorect migration path would be.
I'll keep you updatedt once I have been in contact with the sfb admin on the onther end.
If you are mid migration and or a Teams admin you could raise a ticket with MSFT re the issue

Do you own both the teams config and the SfBS config?

If the end state is to get to 100% teams in a reasonable time it might be worth living with the pain, but if you are saying Teams/SfBS for a while worth trying to hunt down the issue

Did you ever get a fix or an root cause for this please as i am experiencing the same issues between SFB2015 and Teams @TomArbuthnot 

In our case, we believe it was some type of deep packet inspection running on a firewall but we don't have exact proof since the customer decided not to troubleshoot this any further. From sfb CLS logs and wire shark on edge servers we saw the following:
In a bad example (with Diagnostic code 500/16825) we are not getting "ACK" message from Microsoft 365. Comparing it to a good IM example, we do get "ACK" message but there is still a 14 second delay sometimes.

This makes us think there is possible packet inspection going on on firewall side but we didn't have access to firewall to check that.

I'm currently looking at a similar issue.
Tenant 1 is Teams Only (upgrade from hybrid Skype for Business) - unable to communicate with multiple external Skype for Business estates.
Tenant 2 is Teams Only - able to communicate with the above external Skype for Business estates.
I'm performing the Tenant 1 and Tenant 2 tests from the same machine/network. Microsoft say the issue is with the external Skype estate(s). Sounds like a config issue with Tenant 1?