I play on Oasis (with two other 6-boxers, of which one i'm good friends with). I've only caught crap a few times from /lusers and I just heckle them, /report them, and go along my way. The GMs and Guides on Oasis have never given me any trouble about boxing and most people I meet are pretty cool about it. I hear the same from the other two 6-boxers I know.

If you meant which zones... I'm bringing up my third 6-box teams and have pretty much hit every zone in-game and done almost every quest (except harvest & craft quests) with the exception of high end TSO quests.... That one zone where you have to bounce around the air currents and capture the black balls, while the rest of your team fights the mage at max range and if you miss 6 black balls your dead... yeah... f' that. Otherwise, when you hit lvl 10, just disable combat xp and start questing. Wikia has a great 'timeline' you can follow.

And to answer the original question... I was able to 6-box all of the T1 & T2 Kunark Raid zones as the MT Group or a DPS Group. I had a very understanding guild and we accomplished much. Once you get into the T3 Zones and higher, there's just too much running around for a boxer to do the job. Maybe if you were 'overpowered' for the zone, you might can do it... but as it stands, I think the max Raiding any 3-6box team can pull off will be the T2 Kunark Zones.

I don't know of anyone who's boxed Veshaan's Peak (2 or more toons)... and I'm fairly certain boxing a TSO Raid zone is out of the question... Please chime in if you have data that disagrees!!! (cause I wanna try one day)

g'luck