I use email for both talking and scheduling.

When I started therapy a year ago, after a few sessions I realized that I'm holding in a lot of important information that could be beneficial. So one day, after a session, I emailed my T and asked if it was okay to use emailing as a way to get these important thoughts off my chest. My T was delighted I even asked. So for maybe 5 months out of the year I've been going, I used emailing a lot because certain things happened and I needed T in that moment. My T never ever minds it and after every session, even now, says that if anything comes up to email. I haven't emailed in a while about my thoughts but I do email about scheduling and T does the same.

You can always ask about it like I did. My T did give me the cell number for a certain occasion but once it was over I never really used it because my T never said that I could call on that number or not.