In bad weather, my email provider often goes down, burping out old messages days later. Emails do get lost, even under the best of weather.

I think that you can look for evidence of caring in what he does during your sessions, or you can look for a lack of evidence in the absence of an email. I can't imagine finding that my T returning an email that took 20 seconds to say "sorry you had an accident" could somehow trump the importance of the lovely way he listens to and understands me during every 50 minute session, for over 2 years now.

It is up to you to decide how you want to interpret a lack of response (or a delayed response) to an email. But you don't have to interpret it as a sign of a lack of caring.