I expect that the problem is that you don't have an SPF record set for server.cbs-canon, so make sure that exists and allows the same sources as cbs-canon. This is gmail though, so you can't expect it to behave well. I'd also note that your DMARC has p=quarantine, but gmail is acting like it's reject.

gmail - This message does not have authentication information …. !&p=676b54d86bb69a0cJmltdHM9MTY1OTEyOTQzNyZpZ3VpZD0yZDNkOTk4MS1jNmJhLTRjM2EtOWVjOS01MjgwNTBjMDQyNjkmaW5zaWQ9NTEzMg&ptn=3&hsh=3&fclid=d2a19171-0f83-11ed-a800-3c306723b293&u=a1aHR0cHM6Ly9kZXZhbnN3ZXJzLmNv元Bvc3RmaXgtZ21haWwtYm91bmNlLXRoaXMtbWVzc2FnZS1kb2VzLW5vdC1oYXZlLWF1dGhlbnRpY2F0aW9uLWluZm9ybWF0aW9uLW9yLWZhaWxzLXRvLTU1MC01LTctMjYtcGFzcy1hdXRoZW50aWNhdGlvbi1jaGVja3Mv&ntb=1. This usually guarantees that your PHP mail via postfix will not be rejected because of spam issues. You can configure postfix to route mail through an SMTP server of your choice or through Gmail's SMTP server. +all Do not to use this option, this tag allows any server to send email from your domain. Postfix Gmail Bounce This Message Does Not Have Postfix Gmail Bounce: This message does not have ….

Email bounce back message gmail