Are domain pushes safe?

theoretically speaking the guy can claim the account back as if it was stolen - being a person who registered account he can easily ask the registrar to do so and they would because they have his IP and initial reg data (name, address etc) in their logs - not yours. if the name is of considerable value for you i would push it to my own acc or transfer it out immediately. and keep the proof of payment... generally its bad idea to take someone elses account with domains - it doesnt change domain ownership explicitly as it would in case of push/transfer..

well he registered it with my email id. So i don't see how he could claim it back.

Depending on the registrar he could of set secret questions and answer them. There are procedures in most cases in case you "lost access to that email". I would just make a new account and push them into that one.

Which registrar are we talking about here? If you are worried about it transfer the domain to another registrar. You won't get a year added but you will feel safer.