Help with email activation, but not as the term suggests

Hello! I've been a casual reader of warriorforums for awhile now, lots of great information here; some of it inspiring stuff.

Well, I finally have the reason to make a user account now, as I am embarking on a little business venture of my own. And yes, you guessed it, I need some advice
I did search before I decided to post, but the term "email-activated subscription" of course usually brings up pretty much the opposite of what I'm trying to do, which hopefully will be clear from the ensuing onslaught of verbal diarrhea I am about to, and tend to, release.

My needs are simple.

I want to add new subscribers to an email list _based_ on a received email (not empty), as well as determine certain criteria; and add that alongside the subscriber information while I'm at it; by the _contents_ in it.
This received email comes to a specific address under my control (which is external, and accessible, via SMTP/POP).
I will then start a series of autoresponders (4 of them, 2 event-activated and 2 timed) per subscriber, which of course will email them.
Now I know GetResponse can do most of this, but I fail to see an email-activated subscriber option. arpReach says it can do it, albeit from an empty email only it seems.

Question the first: Can anyone recommend an easy way to achieve this (my main issue is with adding subscribers from a received email without prior existance in the subscription list)?
Is using arpReach+VPS overkill for what I'm trying to do? Can a solution be found with an online service with or without a nifty hack? (I thought of how I would script it in python, but my python projects have a tendency to start out good, and begin to fail once I reach a certain level of complexity... i know ... i know ... design patterns and principles, but hey, I'm self-taught so I've got decades of bad habits.. leave me alone!! -_-# )

Question the second: I only need to send about 1000 emails per week at this stage (about 250 expected subsribers) so I should be fine with just my email hosting provider correct? (easydns.com) I am not doing spam or importing dirty lists of emails, the subscribers expect what they're receiving; so in terms of scalibility how far does everyone think I can push those numbers?

Thanks in advance for everyone that can be bothered replying to this madman.