Producers are particular individuals.
Contacting them can be have undesired effects.
This is largely in part to the fact that when contacting Producers, the artists, customers, and fans tend to enter a conversation in a non professional manner.
People need to realize this is a business, and the email and/or Phone number you are contacting is for business.
If you get straight to the point, and talk business first, then there opens up room for casual conversation afterward.
So if you intend on getting a response from a Producer, keep in mind that they are most likely contacted a lot, by non professional individuals, and it would be a breath of fresh air if you contact them with a goal in mind, and get straight to the point.
If you are finding your emails, calls and texts unanswered, rethink your approach and try again.
If you are a serious artist, you will be about your business, and keep it moving.
Professional minds think alike.