Greeetings,
I do have the same problem with IE 11. We are using Mattermost Team Edition 2.10:
Build Date:Mon Mar 14 20:45:23 UTC 2016
Build Hash:f189bc2073cf800c5f4506a69bdb51d7065269bf
My IE version is:
11.0.9600.18230
P.S.:
It works correctly on Chrome...