I have one client on CPanel server which routes all of his mail to another mail server (exim) if the e-mail comes from another server it goes well, but if e-mail is from my server it doesn't reach destination, what should I do to fix it? (MX record on my server DNS directs to clients exim server)

remove the domain from /etc/localdomains

But wouldn't it break other things in CPanel regarding this domain?

No, it shouldn't.

Originally posted by linuxmav
remove the domain from /etc/localdomains

I'm afraid it hasn't worked, I removed that domain name and restarted exim, but I still can't send e-mails from my server.

Remove it from /etc/localdomains and add it to /etc/remotedomains

Originally posted by coight
Remove it from /etc/localdomains and add it to /etc/remotedomains
I'm afraid it still doesn't work. The error is still " unrouteable mail domain"

dig domain.com post the output.

Originally posted by coight
dig domain.com post the output.

But how to show mx output in dig command?

dig mx mydomain.com

I've checked MX record is sat correctly to MS exchange mail server. (Otherwise it would be difficult to send e-mails from outside my server, but now it's possible)