Why my email sent using another domain goes to spam?
I just installed my mail server by following tutorials below:
How to Install and Configure Postfix as a Send-Only SMTP Server on Ubuntu 16.04
How To use an SPF Record to Prevent Spoofing & Improve E-mail Reliability
How To Install and Configure DKIM with Postfix on Debian Wheezy
On the server that i installed mail server, i using 2 domains (domain1 and domain2) with different record for each domain (TXT, MX, NS, A)
I test sent my email using standard PHP mail function using domain1 and that's successfully not goes to spam to Gmail.
But, when i test sent email from domain2, the email goes to spam on Gmail, where 'mailed-by' on email detail is using domain1.
So, how i solve this? Thanks before ...