I would like to create a segment of people how have opened at least three of the last four of my emails. The only option for creating segments is "AND" or "OR" for all emails but not three out of four. I am hoping someone might have a suggestion on how to do it.
You can download a performance summary for all who have opened each of the four mailings in that campaign -- then, with a bit of sorting and Excel wizardry, you can identify who has opened at least three of the four mailings. We recently gave our compare mailings tool a facelift, so you can read more here about using that feature.
With that being said, I would definitely recommend looking at some of your other response metrics, like clicks, so you can paint a wider picture of engagement. This means that while you can analyze open rates, clicking on links in your mailing is also an important metric, as it shows a much stronger action. Feel free to take a look at this Resource Center article that has a great rundown of understanding your response numbers.
Just give me a shout if you have any follow-up questions on this!