I think it is the amount of time and energy you spend on this and where you get with it. I definitely used my therapy more as a distraction than anything else and that was a big factor in why it wasn't helpful. I wish the Ts had pointed this out directly! Maybe one way you can approach what sounds to be a bit of being stuck is going back to the original problems, goals, whatever you brought you into therapy. Does this email thing relate to it in any way, or to any other issues you want to improv in your life? If not, it might be that you are using it as distraction to work on more important things. A motivation for avoidance can indeed generate strong preoccupations but can trick the mind to believe that the content of the distraction is important somehow, while what is more important is that it is a tool to avoid addressing other things.

If this rings true in any way, I would ask myself what it is that I am avoiding so much and create "issues" to cover them. People often say it is closeness and something about the relationship with the T, but I am not sure that is also not a distraction in many cases... while real life problems remain unresolved. I am not suggesting this is the case for you, just bringing up as something to consider when you feel disappointed.