I have to submit my taxes by mail, do I attach a copy of my W2 or do I send the original?

Either a copy of the W-2 or the original would be acceptable.  So just send a copy and keep the original with your tax records.

If you are going to mail your return it will print out with mailing instructions that tell you what to include and where to mail it.

When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s.  Send a copy; keep the original for your records.  

Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.

Remember that federal and state returns must go in separate envelopes to different addresses.