What do you mean?
Amended returns (1040X) can ONLY be printed and mailed to the IRS by you. You cannot mail a return by accident. Amended returns can never be e-filed reguardless of what year.
You also can only amend (or file) 2017 return now using the CD/download desktop software on your computer. Only 2018 tax returns can be completed online.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**