For those of you whose T's have changed boundaries without any notice or without you having done anything majorly different what did you do?

I'm mainly talking really about things like replying to emails and then suddenly not doing that anymore without there be any change on the clients part. E.g I used to write an email to my T once a week between sessions to help get my thoughts down about the previous session. He would read it, acknowledge it and then we might usually talk about some of the things in the next session, generally only if I brought them up. It's always been helpful to get my thoughts down as I was finding it really hard to wait a week between sessions to tell him some feelings/thoughts about things that had come up in the previous session. He would usually just acknowledge it with one line saying something like 'Hey...Got it. We can talk more about our next session'. Although I would have loved a more in-depth answer he doesn't do therapy by email which I understand so was more than happy with this one line as it made me feel heard. The last two times I have emailed he has not sent any acknowledgement although has brought up the email in session and we have discussed. Nothing has changed except for his lack of acknowledgement. The email is never more than 10 lines long (I make a point of that) usually just a main thought or idea.

I know everyone will say I need to bring it up which I plan to eventually but I just don't understand why T's do this sudden change and I have seen it happen a lot. I understand when a T has perhaps been too lax on boundaries, realises their mistakes panics and pulls back (It's not okay but I see that happening) but what about there appears to be nothing like that? Is it a technique/intervention type thing? Is it that they were consulting with someone and they made them think twice about it? It's just very confusing.