I'm experiencing some issues that I thought were something normal, or something that you could expect when working like this, but I think that it is something that should NOT happen.
We own a dedicated server, where we host some sites we develop (around 80 right now). We usually host both email and web page in the same server, but recently we had two customers who wanted to host email in a different place. The first one has its own server with proxy, and the second one is waiting the previous company to change DNS values.
The problem shows when we try to send an email from ANY domain hosted in our server, to one of these domains. From Outlook, the error is something like "no such user found", but the REAL problem comes when a PHP script (usually a contact form) tries to send the email. This mails get simply lost, and the customer never receives them.
My question is: What do I configure, or how do I do so my webserver looks for the real DNS, instead of trying to send the mail directly to the local domain?
I just tried to look into webmin options (sendmail), and saw nothing that could give me a clue.
About local DNS... not sure about what you are talking about. We just host the server on a hosting company. If there is a local DNS configured on their datacenter... I dont know. Here, at our office, we have a simple ADSL connection with no proxies or special configurations. Mails run perfectly always, but when Domain1 and Domain2 are hosted on the same server, but Domain2 has email on a different server, Domain1 is unable to send mails to Domain2, as the server looks up locally, instead of going outside to check the REAL dns, pointing to another server.
And as said before, not even the server itself is able to send mails to this domain, because it tries to send it to its local domain user (that does not exist) instead of sending it to the server that is really hosting the email.
You'll need to tell 'Plesk' or your POP system that this mailbox for that domain is NOT a local one, so the messages get delivered.
I know how to do this on other panel, not plesk, as every panel can use a different mail-pop system.
Well after reading this I headed to Plesk in case I see an option to do that, and guess what... I had the idea of disabling mail for those domains. Just, "Disable" it, nothing else (it was enabled but without any account inside it). Now I tried to send an email from my Outlook and I got no errors, so I guess it went out. I'm not sure if it arrived (I'm awaiting a customer's confirmation), but at least it went out, it seems.