My dh’s relationship with his mother has been on a downhill slope for years and years. It’s now got to the point where he has told her he doesn’t want to see her anymore.
For a bit of background, her treatment of him is bizarre. She comes round and makes nasty comments about our house/ our parenting/ our food/ our children not doing the 11 plus/ etc etc etc and it’s horribly awkward when she’s here, but it’s like she has no consciousness of it and wants to come round constantly, then cries and uses dreadful manipulation if we say no. When, for example, we moved half an hour away she phoned us up and wailed down the phone about how we have abandoned her and started bringing up dh’s beloved deceased dad, which really upset him.
Anyway, back to now. She left it a few weeks after dh said no more contact and then went back to emailing him as if nothing had happened, asking to meet up at Easter. I stupidly offered to take on the burden of her emails as he is stressed out of his mind with her constant messages to him asking him to call her or come round. (She is blocked on his phone).
I’m now getting battered with emails instead. I said to her that she needs to respect his wishes and leave him alone. I got a manipulative email back saying dh is obviously mentally unwell and she hopes I get him the help he needs!! 
I simple replied saying he is fine thanks and to respect his wishes and that I won’t engage with her further.
Personally I think we need to block her on email too but dh thinks we need to read her emails in case she threatens us with legal action over seeing dc.
I’m now horribly anxious waiting for her next email to drop!