Where do you see the MX record? The MX record is mx.byetcluster.com. But the email only contains references to sendmail.free.byetcluster.com. Which is a different subdomain, pointing to different servers.
The domain name byetcluster.com refers to the “ByetHost Free Hosting Cluster”, which is an internal name of the platform we’re using. Hence why you may see us suggest nameservers with the domain byet.org.
But sending emails don’t show MX records. Like you must have read in the article you linked to:
MX records only affect which email service is responsible for receiving email. MX records do not control who can send email for your domain names. Sending email is never affected by the MX records of a domain.
We try to make it as clear as possible that MX records do not affect sending email. Which we try to make clear, because MX records do not affect sending email.
The raw message says quite clearly what the problem is:
[email protected]: host al-ip4-mx-vip1.prodigy.net[144.160.235.143] said: 553
5.3.0 alph775 DNSBL:ATTRBL 521< 185.27.134.28 >_is_blocked
If you Google “DNSBL”, you’ll learn about a method which blocks email providers. Clearly, the sending IP address is blocked. Which is an ongoing issue. This affects all websites on all domains and all accounts. And it’s in no way caused by your MX records.
So, in summary: yes, problems with email sending are an ongoing issue. But like we clearly describe in the support article you linked to, MX records do not affect email sending, and the MX records you’re trying to delete does not affect any email on any of your websites.