Nice mod, thanks a lot!
I've been searching for an auto responder mod for several days now, found a few which were for SMF 1.x only, one which claimed to be compatible with SMF 2.x but in fact it did nothing, and this one which unfortunately is limited to SMF 2.0 only due to package-info.xml settings.
I gave it a try and changed the compatibility setting from "2.0" to "2.0 - 2.99.99", installed it and it works perfectly on my SMF 2.0.7.
Thought I'd share it here if someone likes to benefit from this too.
Best regards - Mike
[Mod edit: Don't redistribute this without explicit written permission from the author - lve627]