Additionally, the fact that an ROV couldn't engage the BOP using its onboard HPU (the so-called "hot stab") also casts doubt on the claim that an acoustic trigger would've done any good.

I checked out the specs on Mail from Apple's website. The only reference to Exchange I could find was support for NTLM v2 authentication. Being able to natively authenticate and being able to talk Direct Push or do RPC over HTTPS with Exchange are two very different things.