In such a case you either need to e-verify or send a physically signed copy of ITR-V to the tax department after e-filing your tax return.
Search your inbox for an email from the Income Tax Department.
Download it->print it->sign-> send it to the address mentioned in the document's last line.
The password to open the ITR-V is your PAN in lower letters followed by DOB (ddmmyyyy). Eg: Password for the following details: ABPPA1234D and 01.01.1990; will be abppa1234d01011990
Instead of physically sending your ITR-V, you can also e-verify it (if 120 days have not been elapsed) since filing your return.