Hi,
i have followed the linode guide step by step:

https://www.linode.com/docs/email/email ... -and-mysql

i have added two virtual users:
theking@kingofmagic.it
noreply@kingofmagic.it

and two aliases:
info@kingofmagic.it
trial@kingofmagic.it

Then i have tried to send some email test to:

http://www.mail-tester.com

and pass all test with a score of 10/10, but when i send an email from "noreply@kingofmagic.it", "info@kingofmagic.it" or "trial@kingofmagic.it" go in the SPAM folder instead if i send an email from "theking@kingofmagic.it" go in the normal INBOX, i have searched a lot on the web and i have find this tool:

http://mxtoolbox.com/domain/kingofmagic.it/

That give me some warning, I do not know if this is somehow related to my problem.

Anyway i don't know if helps but this is my postfix conf in main.cf:

myhostname = kingofmagic.it
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = kingofmagic.it
relayhost =
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all

anyone can suggest me something?

Are all of your DNS records set up properly? Be sure to make sure your rDNS entries and FQDN on your server are set up correctly.