How to make optional fields more subtle to reduce its usage?

How to make optional fields like email a bit more subtle? The intent is to have minimum prominence for the email field and reduce its usage. The reason why we can't remove it is that lead capture fields are decided by the clients and they force us to keep it optional instead of removing it.

There are the 2 options we have: 1)

2) The below image has been labeled as Email but we will keep it as Email (optional). It's a checkbox which will open text input similar to 1st image.:

Which of the two option is better in terms of:

1) More people should understand it's optional and skip it if they want to.
2) user experience wise