I don't think there is one absolute answer to your question. I really think it depends on the person in therapy and the therapist and the relationship that they have.

I understand your concerns about this go deeper than this question about emails though and I can see how worried it makes you. I feel for you.

For what it's worth, I don't think any topic is any less worthy to be discussed than any other and I don't think there is a golden rule about any of this stuff. If it is important to you in that moment, then it is important. Sometimes you might not need to email about it, but that doesn't make it any less important!

I think your fear of being "too much" is understandable and I do really feel for you. But, again, for what it's worth, from my point of view, even if you did happen to send something irrelevant or silly or too many emails, it wouldn't make you bad or toxic to your therapist. It wouldn't make you bad or toxic full stop.