I have a one-ip server with multiple virtual servers running. I added a MX record to each domain so I can receive mails on the server and I receive them in Webmin (mail UI).
Now I need to send emails through each website with PHP, without using an external SMTP.
I copied the postfix configuration on domain1.com, then domain2.com and the button disappeared from domain1.com.
I receive the email as spam when sent from a domain that had postfix deactivated like I said above. How can I setup emails to be sent by the server and not worry about clients receiving SPAM ?
I thought about using Mailgun, which I tried with a postfix-relayhost but this will work for one domain only, since Mailgun works per domain.
Edit : I have to add that I don't use BIND, it's disabled. I use my hoster's DNS, which makes simplier to manage each domain on it and less routing/config ! I might have a solution but I need someone to confirm. By adding each domain to the DKIM page into the 'additional domains', I receive emails signed and sent from said domain and then adding the key as a TXT record. But I can't know if this is considered SPAM or not to many email receivers. How can I learn about securing emails ?
Thank you !