That sounds like a scam. You don't have to provide your 2017 AGI if you file your tax return by mail. Who is the email from? The IRS does not contact taxpayers by email.

I would not reply to that email, and certainly not click any links in the email or open any attachments. If the email says it's from the IRS, forward it to phishing@irs.gov

See the following link on the IRS web site for more information about email scams.

https://www.irs.gov/privacy-disclosure/report-phishing