Teams Phone can't sign-in behind pfsense

[n0npr0phet]

Hi,
We are unable to use Yealink Microsoft Teams phones from behind pfsense on our LAN. If we use WiFi via MiFi it works fine. If we take the Teams Phone to a non-pfsense location it works fine. If we take it home but we have a vanilla pfsense at home it fails again.
It fails on the sign-in when it fails.

Packetcapture seems to have an unsual amount of this type of traffic.

The 10.77.1.75 address is the phone while the other ips are Microsoft.

We don't see anything in the firewall logs.

Thanks

[stephenw10]

Looks like it might be an MTU issue.
Check other successful TCP connections, do you see the same packet size?

[n0npr0phet]

Thanks @stephenw10 That was it. A collegue had reduced that because of a packetloss issue. Works fine now everywhere. I really appreciate your fast and rewarding answer.