I send a file of my mod and it had to go under greenlight. It got rejected:

Invalid file extension, expected jar, litemod.
If you have any questions please contact our support team https://support.curseforge.com.

The file that I made was .jar
Can anyone explain me what's wrong?
Did you experience the same problem and did you solve it?
I tried to contact the support, but the captcha doesn't seem to work

Thank you in advance