It may be that he is having regrets about the break up and he still cares about you and this may be his way of wanting you to contact him so that he can talk to you or he may be finding ways to find closure because he is finding it much harder than he thought to get over you. He may even want you to still care about him the way he cares about you. You have several choices, you could contact him and ask him what he meant by the email and what was the point in writing after no contact for 3 months. You could also ask him to meet you for lunch or some coffee to discuss the email or you can leave it alone and go on with your life the way you have been for 3 months before he contacted you. If you still care about him also then maybe it would be a good idea to write him back and talk about things but if you feel that it will get you no where because he did say "if u ask for us again, I'd say no" depending on who broke up with whom, if you broke up with him he may be wanting you to ask him to get back together so that he can be the one to reject you if he is feeling rejected. If he broke it off then he may be finding it harder to get over you and needs this as closure to move on.
Either way he has already told you if you wanted to get back together he would say no so with that being said I would just move on and not answer the email and just carry on as you were before he contacted you. If you have anything to add just click reply it is free.