As mods :-mod=@agm;@CAF_AG1.5;@CBA_A3;@JSRS;@RDS_Civ;@task_force_radio;@weapons;@A3MP

Hello,
if you disable all mods and try to join any public server with vanilla data (e.g. King of the Hill), does it kick you as well?

No with vanilla data everything is alright. I think it's because of the mods, but i wonder why i dont get any Error Message why it doesnt work!

It could be because the mission is not initialized yet. However, it seems that the problem is caused by community addons and that is a problem we cannot do anything about.

Here is a easy recipe for reproduce this issue:

1. Have some mods installed to Arma3 Launcher, like:

@CBA_A3;@ASDG_JR;@Ace;@AllInArmaTerrainPackLite;@RHSAFRF;@RHSUSF;@vt5;@ace-comp-stuff

2. Have same mods installed to server (Windows, 1.48)

3. Connect server. Load missing, which uses those mods and verify you can go to the Multiplayer setup.

4. Exit game

5. Remove one mod from Arma3 launcher, like RHSUSF

6)Connect server, load missing which uses those mods and you are kicked out from server.

From Arma3 console log:
18:50:23 Game Port: 2302, Steam Query Port: 2303
19:34:40 <user> uses modified data file
19:34:40 Player <user> connecting.
19:34:42 Player <user> connected (id=).
19:34:56 Player <user> disconnected.
19:35:43 <user> uses modified data file
19:35:43 Player <user> connecting.
19:35:44 Player <user> connected (id=).
19:36:03 Mission co@ 8 RHS ACE AB Saattue Valtatiellä read from bank.
19:36:03 Player <user> disconnected.

Also, there is no error show to the Arma3 game, nor I cannot found any hint from Arma3Server.rpt.

Proposed procedure (like already in Arma2:OA)

1. Missing PBO / mod / file / reason for exit written to Arma3 console log with timestamp, player name and mission to be played.
2. Error message to be shown to end user with missing PBO / mod / file / reason for exit.

I second Sami's suggestions.

People running modded servers currently have no way to determine why someone gets kicked off their server. As Sami says it just shows player .... disconnected in systemchat, but Arma 3 doesn't show to the person being disconnected why he has been kicked off the server.