Spam with postfix

SYSTEM INFORMATION
OS type and version centos 7 min
Virtualmin version virtualmin 7

how we can configure postfix to not sending spam emails

thank you

What do you mean ?
post up some of you mail log so we can see what you mean …
or do you mean mail sent from your server ends up in the recipient’s spam folder ?

yes like that, but gmail and yahoo rejecting my emails

thank you

You are using all the required filters like spf dkim & dmarc ?

is there a tutorial somewhere to configure those?

thank you

Not a tutorial, but see:

And also: