e5 after e4, e6 in the french defense

What is the best way to punish e5 after e4, e6 in the french defense. What is the rationale behind the move e5 in this context anyway?

I'd advise against taking up a mindset that any move that doesn't look to be a book move can be "punished." It is easy to develop tunnel vision and underestimate the point of the move and your opponent in the process.

The rationale of 2.e5 is most likely that it gets a French Defense player who relies on memorization out of book and into unfamiliar territory. I don't play the French but if I were black, the two moves I would consider are 2...d5 and 2...c5. If I play 2...c5, I'm looking at preventing the d4-e5 pawn chain and will prepare to attack the e5 pawn with moves like Nc6, Qc7 and maybe Nge7-g6.

2...c5 is strong. Also 2...d6.
2...d5 just transposes to the Advance Variation after 3 d4.

Just play 2...d5 anyway. If 3.exd6? Bxd6, Black is already ahead in development.

No french player with any sort of idea what they are doing would be concerned with 2e5. It is more white announcing with a fanfare, they are a weakie, similar to most Bb5 moves.

2...d5 will probably transpose to a regular French advance, 2...d6 is just fine, and a sane positional choice would be 2...c5 (anticipating d2-d4) followed by ...Nc6, ...Qc7, ...Nge7-g6 when the e5 pawn is more of a liability than an asset.

@6
2...d5 sort of admits that 2 e5 is fine and allows to transpose to the Advance Variation
2...c5 and 2...d6 are the only tries to punish white for 2 e5.