unboxed my xbox and after green screen it says "contact customer support e305 "

An E305 can be nasty. It's either an update failure, typically due to a bad connection, or there's something wrong with the HDD. If it was me, I'd take it back to the store and swap it out if you just got it.

Ouch, that's not good. Please try holding the power button on the console for 10 seconds until it shuts down to see if that resolves the issue.

If that doesn't work then I would recommend returning the console to Walmart for an exchange instead of contacting support and sending it in for a possible repair.

Good luck.

I just received my Xbox One in the mail today, and I plugged everything in and turned it on. The green loading screen comes up, but the screen then goes black with the text, " System Error. Contact Xbox Customer Support." with the code "E305 00000001 80075CFE".
I searched this code on the Xbox Support website, and no helpful info came up. Do I just need to send it back, or is there some magical Mr. Miyagi crap i need to do for it to work??

My son has the same problem, brand new Xbox one! Turn it on to the green screen for a few seconds then a black screen saying contact Xbox cust service, system error code e305 00000001 80073cfe

Can't do n e thing with the *** thing, tried turning it off, unplugging it but makes no difference, seen the offline dignostic stuff but a pain in the ***, got better things to do Christmas morning, n e one found a solution to this??

Germany - same issue first green screen, after contacting support it's black ^^