one of my client recently took 1and1.com's virtual dedicated server. everything was working fine, and to avoid server load we are using gmail standard business email hosting for our domain hosting. It works fine, except that when a PHP scritp try to send email to internal domain the email never gets delivered nor it stay in queues.

when I do dig -MX for domain server clearly show gmail's MX record so server DNS is serving well. So what can be the possible cause of error and hence what is the solution for it ?

I read somewhere in plesk documentation that to avoid spam, they have some check on sendmail version and that check doesn't consider the MX record but check internal domain user list to see if domain user is valid or not, which in that article says is incorrect. But I am not very professional in managing server and hence I didn't understand that fully. Probably someone out there can help.

Could be you're attempting to mail out through the local machine and it believes it's the end destination for the email. How exactly is he attempting to send the mail, there are a multitude of methods to do it from most of the scripting languages.

Hello,

We are using simple mail() function of PHP. And that mail function send email to anyother domain that is not hosted on this server.

I try to use sendmail through SSH to send email to internal domain and it fails, but it send to other domain as PHP does. So I believe it is sendmail configuration problem.

Maybe this give an idea of what I mean

http://kb.parallels.com/en/4420