I have this scenario:
I run a Smartermail Server with several domains.
A client migrated his domain (lets call it example.com) to another host, but kept the domain on my server as a secondary MX, so if the first fails, he keeps getting e-mails through my server.
The problem is that even with the MX records properly set, when any other client domain that is on the same server tries to send a e-mail to example.com, the e-mail is sent locally, without checking MX records to send it externally.
Is there a way to fix it?
PS- If I was not clear enough please let me know, english is not my fisrt language.