Is there any free email providers?

Hello.
My server IP is blacklisted for emails, and all my emails land in spam specifically for Gmail.
I want to change the server of the entire web hosting account, is there any free alternative that I can use?
I can use Zoho mail, but that is for each domain zoho offer 5 free email accounts after MX record change, but that is not efficient, I want to change the entire server when I create an account for a domain so that email services are used by default.
need guidance, how I can achieve this, and which service provider is best which can work with CWP itself for all accounts?

thank you.
regards.
hassan.

You will have to get a backup mail exchange -- one that does store & forward.
https://bobcares.com/blog/backup-mail-exchanger/
I don't have any particular recommendations, since it's been more than 12 years since I've needed one. Last one I used was:
https://www.dynu.com/en-US/Email/StoreForward

thank you for the anwer. one more question, is their any resource to follow to implement this in cwp pro, so that all email's use the backup exchange server and email pass through for any account without landing in the spam?

can you share, how to implement this on cwp pro for postfix?

you can create your own email server in few dollars take a server from here https://cloudfanatic.net/
install cwp complete the email setup and use it as smtp relay