In a word, no. Really and truly no. There are very few places for a shirt with tails to be untucked, and none of them involve the office. Keep the tails in at the office. Period. If you really feel like you need to experiment with an untucked dress shirt, try this: Get yourself a suit with a really modern and semi-deconstructed cut and wear it after hours with the jacket open, the shirt untucked, and the cuffs undone. You have to have a tall and lean build for this but if you can pull it off you will have that long cool look that so many guys strive for and so few guys find. Talk to your tailor about it and try it out in the store before you buy. If it works for you then consider yourself one of the chosen few and wear the look with pride.