Your question was pretty tough to follow and understand. I understood this: You got an auto-reply from someone's email, but you never sent an email to them in the first place. And you're thinking that something else sent an email as you and you want to know how that is possible. My response is based off of that assumption.
Mail forgery is pretty simple. Anyone can set up a SMTP mail server that sends email out from firstname.lastname@example.org. Most mail servers will reject it, based off of PTR and MX record checks (I believe) and they'll see it came from an IP address that doesn't quite match up with the MX records. However, I think a lot of mail servers will accept mail if it sees the "from" part is coming from it's own domain, or if the content of the email is simple (text only, no links).
That is how I can get mail from all of my servers without them being "official" mail servers for my domain. As part of my business's application, the users have the ability to email themselves content from certain parts of our app. When our mail server sends the email out, we forge the email with the user's address in the "From" part, so when they get the email, it looks like it came from themselves.
At any rate, to directly answer your question, this process can easily be scripted and put in a cron job.