I do think it is important to get expectations lined up. I am personally not a huge fan of email for things other than scheduling or to get something away from me due to the sense of immediacy I think it instills. I don't want a response.
Also, for example, I tell students I will respond to emails within 48 hours and that I don't check email on the weekend. That way the student knows it is not about them, but about how I operate. I also will sometimes tell a student they need to see me in person - that I do not believe I can respond by email for their issue.
I don't text with my students. I would not text with a therapist.
If it works for both parties, then great, just not something I would do.