any of my clients is not able to send mail
when i try to send from telnet i am getting
220 lin.xxx.com.tr ESMTP
MAIL FROM: firstname.lastname@example.org.
RCPT TO: email@example.com
550 sorry, no mailbox here by that name. (#5.7.17)
when i try to send from roundcube i get :
SMTP Error (504): Authentication failed
i should not find any log on /var/log/maillogs about this send operations.
but my clients can get mails from remote servers.
i try to disable relay -> not solved
i try to disable firewall and selinux -> not solved
i try to change mail server to postfix -> not solved
what should be the problem