I don't know how you can take a statement like that any other way than as an invitation to email. It's very straightforward. A therapist is not going to say something like that if they are feeling conflicted about it. It's not like being told to go ahead and have the last slice of pizza, where there's a good chance the other person is being polite and hoping you say no.

I wonder...what would your therapist have to say to make it sound clear to you that they would like you to email (or are fine with emails)?