I have two different companies set up in one instance of InvoiceNinja, installed on a subdomain proposals.domainA.com. Each company has a unique domain and a unique email to match their unique domain. The first company I set up has the sender email that matches Domain A, and it sends emails via SMTP without any problems. The second company I have set up has a domain for email for Domain B, and I’m finding that email is not getting delivered to iCloud email addresses.
How can I configure so that Domain B will work under the subdomain for Domain A?
Incidentally, I used MXToolbox and found that it cannot find a DNS record or a DMARC record, but I don’t know which record I need to add where considering I’m dealing with two domain names.
Here is a video showing a brief walkthrough of my two companies and how the email is configured:
Are you using your own local mail server? From the video it appears you have configured two outgoing mail servers on the one instance. There will be inevitable issues with this.
One basic check on incoming email is to check the sending servers rDNS record. If it does not match the from address domain some receiving email servers will automatically mark the email as Spam. You can confirm this by inspecting the spam email headers to confirm.
Aside from this, correctly configured SPF, DKIM and DMARC records for BOTH domains will help improve your mail delivery %