No. Not unless they responded and a message room has been opened.
But, clients very seldom engage with anyone other than the freelancer they choose to hire. And many jobs go unfilled. So, reaching out to someone who hasn't responded to your proposal is probably not an effective strategy anyway.
If a client sent an invite or responded to the initial proposal then you can send them messages.
If I really like the project, I'll message an unresponsive client once after 24/48 hours letting them know I'm available to chat and answer any questions they may have about the value I can provide.
Sometimes I get a response amd we end up working together.
Most times, it's crickets.
And I move on.
P.S. I just wish it was possible to permanently delete message rooms that are going no where.