I can only guess at the amount of emails/day it takes for a person to whip up something like this — I got it as a response to an email I sent just now:
[This message was generated by an automated system.]

I am not on vacation, but I am at the end of a long time delay. I am
located somewhere on Earth, but as far as responding to email is concerned,
I appear to be well outside the solar system.

After your message arrives at [domain], I will collect it in my next batch of
incoming mail, some time within the following 24 hours. I will spend much
of the following day reading that batch of mail and will come across your
message at some point. If I can write a response for it immediately, the
response will go out in the next outgoing batch–typically around 24 hours
after I collected your message, but occasionally sooner or later than that.
As a result, you should expect a minimum delay of between 24 and 48 hours in
seeing any response to your mail to me.

If you are having a conversation with me, please keep in mind that each
message you receive from me is probably a response to the mail you sent 24
to 48 hours earlier, and any subsequent mail you sent has not yet been seen
by me.