You’d be mistaken for thinking that Post 390 has a business-casual dress code. It doesn’t, it just so happens that everyone in here looks like they spent the better part of the day in front of a spreadsheet. That’s probably because it serves a competent American menu that pleases just about everyone, and is surrounded by insurance companies and hotels in the Back Bay. Upstairs you’ll find a more formal dining room, but we prefer the tavern area downstairs with a bar and fireplace.