I think there is no objective measure of what is important or not important to email about. It just depends what works for you and your T and how you negotiate it together.

When I started working with my T, she basically gave me free rein to call or email (but she doesn't answer at length or right away). She just said if it got to be too much, then we would discuss it together. Even so, I used to have a HUGE issue thinking whatever I emailed was going to be too much, or not sufficiently important, even when she wasn't complaining about it. She kept saying stuff like "even if you just want some contact or support, that is enough reason" but I refused to believe her!

I think there is a lot of stigma about being "attention seeking" but the reality is that getting attention and contact is a legitimate need, not something we should be ashamed of wanting. Because my T views our work as relational and attachment-based, I think she views staying in touch, even over little things, as part of the therapy (although if it got to be too much for her she would certainly say so). However, other T's may view things differently and therefore have different boundaries.

Anyway, although I used to be terribly concerned about emailing too much, one weekend I sent like 10 (short) emails complaining about very small stuff like fights I got into with my H. It turned out T did not mind at all. In fact she said it was helpful and gave her a window into my world. So the bottom line is I could have just believed her the first time she told me she was OK with it, instead of twisting myself into knots about it...