RFE for OPT STEM extension

[Aarya.]

I have received an RFE from USCIS to provide my employers e-verify number. They have sent a cover letter but no where in that letter can I enter the details. How do I provide these details to USCIS? 

Also how is submitting the evidence by mail different from submitting it online? Can i do either or do i have to do both? Or is one better than the other.

[Attorney_15]

Generally, if USCIS has requested information but they do not provide any specific place that they are telling you to write it down, then you can normally write it on a separate pieces of paper and attach it to the RFE letter from USCIS to return it. Responses to an RFE should be sent by a means to verify the government's receipt, so if someone has an ability and opportunity to reply online or by mail, normally filing one's RFE response online is sufficient.