I tried a few times to use KLM's in-flight wifi which is supposed to be for
text messaging only.  I figure it ought to work for IMAP/SMTP too.
It never quite worked for me, although the price was right.

But, I think that it's a good niche for what are going to be unavoidably
dog-legged high-latency aircraft connections for the various LEO solutions
come to aircraft.