SMTP email using Exchange server from web application

I have a site that uses SMTP to send outgoing messages, but I'm having trouble integrating this with our exchange server.

I have an external company which hosts our exchange server, so when I setup our web site I set in the web hosts MX record to point to our exchange server. Now all emails that go to our domain get shuffled along to our exchange server, 开发者_开发技巧which works well.

The problem is that when I set my webhost to use the custom MX record, it switches off all email services they provide, which includes SMTP email. Now that I am setting up some forms which will use SMTP, it seems like I can't send outgoing mail.

So, with this kind of setup in mind, would it be crazy to assume that if I tell the SMTP server to send using localhost, it would look at the MX record and find the exchange server and use that to send the email? Or should I still be pointing it somewhere specific?

This might sound like I'm asking a question specific to the webhost, but I'm wondering more about the general idea of how a setup like this normally works.

Thoughts?

Generally you just point your SMTP component to the actual DNS name / IP Address of the Exchange server. You don't need to set up an MX record.

Additionally, you need to enable relaying on your exchange server for the server running your site.