Web Form via SMTP

[xenophobia]

I am seeking for advise on setting up the SMTP for my websites.

 

I have two servers. One is mail server and another one is web server.

 

I have more than one website in the web server.

 

All email accounts are stored in the mail server.

 

On my website, I have many enquiry forms. Some on the same domain some on different, but same server.

 

These forms will send an email to the site owner once user submit the form.

 

My questions:

1) Should I configure my script to use the mail server as a relay to send out email via SMTP? Because as I know, if I use the sendmail program in the web server, email that goes out will categorized as spam.

2) If Q1) is YES, should I create one account for each domain? Because I have multiple domain hosted on both server. So each website will use the assigned account to relay email.

3) Is it possible to configure my mail server to whiltelist my webserver so that it allowed it to connect via SMTP without authentication and allowed to set the sender's email differently? If possible, which setting I should look into? EG: SPF.

 

This is a conceptual question. So no hardware or software restriction. I just need some guide on where I should look into it.

 

Thank you for reading!