According to the instructions of the 1040EZ tax form, you cannot use the U.S. Postal Service if you want your last-minute tax filing to reach the IRS before the deadline.
The instructions require you to use private delivery services (such as FedEX or UPS) to meet the “timely mailing treated as timely filing/paying” rule for tax returns and payments.
Sure, you can e-file. Or, you can file for free if you earn less than $66,000 per year.
It is just odd that you cannot use the U.S.P.S. when you are close to the deadline.
I realize using the internet to e-file makes things much easier on everyone. However, some people still need or prefer to fill out the form and mail it.
It is interesting that the federal government won't accept use of the federal postal service to deliver your tax return on time.
Here is the actual section from the instructions: