... are the receiving emails secure too? Basically I'm using Hotmail and I have https turned on, and I know that my outgoing emails are secure and can not be sniffed, but I'm wondering are the receiving (in-going) ones secure as well?

In short: No.

Though most email providers send email over secure connections, there's no guarantee that all the mail and relay servers will use a secure connection.

Also, you'd have to entirely trust your mail service from your client to your recipients client. Any node in between could, in theory, read your email.

If you need to have your email safe, use something like pgp to encrypt your message.

just to add, gmail uses https only to login, then (receiving/sending) is done in plain text. pgp encryption would be a good workaround (encrypt, check, sign, decrypt). also there was addon for firefox to encrypt/decrypt ur gmail messages. also u could use thunderbird to do it automatically, or just do it manually.