In my email sounds better to me. It's probably more a question of convention than of a 'rule'. At any rate, you should say 'I forget to do something'.
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Anonymous1. I forget include you on my email / in my emailI don't think any of these is correct. How about "I forgot to include you in my email."
2. I forget inculde your name / you in my email
3. I forget cc you on my email / in my email