helo/hostname mismatch using domain alias
I have set up my domain to send/receive all mail through my mailbox.org account. I use Zoneedit to mange the domain, and have set up the alias by providing the correct TXT record for the domain. I typically use this email through Thunderbird and can send and receive mail just fine. I have set up SMTP authentication on Thunderbird through port 465 as well.
The problem is that some mail servers are rejecting some of my sent mail as spam. The recipient does not receive my email. Instead, they are sent the following email from their mail server:
Remote-MTA: DNS; mxext1.mailbox.org
Diagnostic-Code: @eclecticvagabond.ca; 550 5.7.1 <Norman@eclecticvagabond.ca>: Recipient address rejected: Mail appeared to be SPAM or forged. Ask your Mail/DNS-Administrator to correct HELO and DNS MX settings or to get removed from DNSBLs; MTA helo: mail145c7.megamailservers.com, MTA hostname: mail545c7.megamailservers.com[184.108.40.206] (helo/hostname mismatch)
Is this a problem with the DNS setup for my domain eclecticvagabond.ca, or something wrong with how mailbox.org is forwarded on my email?