Email address apparently blocked during account setup. Why?

When trying to set up a LibreOffice account using my standard email address I got a message “Email not sent” but was given no explanation. Two attempts failed. When using an alternate email address (which is an alias for the first one) the account setup succeeded. The desired email address was a address (if that matters). Why was it not acceptable?

Email addresses under that domain are blocked. The email provider is (or at least was) not making hard enough for spammers to create accounts there.

Hmm. It would be nice if there had a been a message saying the domain was blocked rather than just saying an email could not be sent.

Is there any published criteria used to determine this blockage? I’m sure ZOHO would appreciate knowing why they are being blocked and would probably work to change the situation. They are primarily a vendor of business “solutions” (including email) and hopefully value their reputation.

Also, it seems a bit odd that my primary ZOHO account was blocked but an alias (using my own domain name but exactly the same email provider) was accepted.

We don’t tip spammer as to why their registration is rejected, just like we have the same message for wrong password and unkown user. The generic message is intentional.

The domain is listed there.

We don’t claim our anti-spam measures are perfect. False positives and false negatives are both inevitable. The point here is only to limit spam while not making too painful for the majority of users. We’ll keep trying to up our games when the rate of false negative increase. At the moment MX lookups sound like a premature optimization.

So I should ask ZOHO to get in touch with and clear this up?

It looks to me that forums that use are blocking legitimate users (which fosters ill wiil).