I don't think the author appreciates how difficult this is.
I think it's trivially easy. Hire some temp workers to do it.
Heck, you could put a note "We send these emails to a lot of people and many are returned to sender unopened. If you reply to this, please type the word 'reply' in the following space to make it stand out from the returned emails and grab our attention : [ ] "
Then filter those out as a priority. That could solve a lot of the problem even without a good mail filter.
Temp workers are more expensive than CPU time. Bayesian filtering would go a long way in cutting out the auto responders, but I agree, the problem doesn't seem too difficult.
If it wasn't too difficult, big companies with loads of money would be doing it, right? Doesn't seem that many are, which suggests that the biggest and best haven't found an efficient solution they think is worth paying for.
I think it's trivially easy. Hire some temp workers to do it.
Heck, you could put a note "We send these emails to a lot of people and many are returned to sender unopened. If you reply to this, please type the word 'reply' in the following space to make it stand out from the returned emails and grab our attention : [ ] "
Then filter those out as a priority. That could solve a lot of the problem even without a good mail filter.