For email, regardless of the spec, I virtually always go with 512 (nvarchar). Names and surnames are similar.
Really, you need to look at how much you care about having a little extra data. For me, mostly, it's not a worry, so I'll err on the conservative side. But if you've decided, through logically and accurate means, that you'll need to conserve space, then do so. But in general, be conservative with field sizes, and life shall be good.
Note that probably not all email clients support the RFC, so regardless of what it says, you may encounter different things in the wild.
