Does RFE come in both email and regular mail? Please Help

My 485 has just been assigned to an adjudication officer, but I have to go oversea for a whole month because of an emergency. In case the IO send me an RFE by regular mail, I won't get it until I pick up held mails a month later, which is too late.

I am wondering if they also send email when RFE, or put a message on the case status webpage? Do I need to call USCIS about this? how do I get to talk to the IO?

Thanks!!!!