"Privacy" means more than one thing in this context.
Mann did not have (and shouldn't have expected) a right to privacy over his employer, the university. If they wanted to read his emails then they could.
But he might have had (and expected) a right to privacy over the general public, or more specifically organizations like the American Tradition Institute.
You can only get from "the university were entitled to read his email" to "the ATI were entitled to read his mail" by assuming that the ATI had that right over the university -- and that's pretty much exactly what the court case was about, which has just been decided in favour of Mann and the University.
So, yeah, support of FOIA laws is doubtless a valid business purpose, but support of FOIA laws did not require the university to hand over Mann's emails. And this has nothing to do with the question of the university's right to read Mann's email.
Mann did not have (and shouldn't have expected) a right to privacy over his employer, the university. If they wanted to read his emails then they could.
But he might have had (and expected) a right to privacy over the general public, or more specifically organizations like the American Tradition Institute.
You can only get from "the university were entitled to read his email" to "the ATI were entitled to read his mail" by assuming that the ATI had that right over the university -- and that's pretty much exactly what the court case was about, which has just been decided in favour of Mann and the University.
So, yeah, support of FOIA laws is doubtless a valid business purpose, but support of FOIA laws did not require the university to hand over Mann's emails. And this has nothing to do with the question of the university's right to read Mann's email.