INVALID REGISTRATION when registering with certain email providers

I can confirm it to - I was able to create an Mojang account in MC website with using my own domain and buy a copy of the game. Thank you. May I ask, what was wrong/broken ?

IMHO: I thing that Moderator of this bug tracker should add error message ( "IllegalArgumentException: Registration failed" when trying to register a new account ) in title of this bug - when Google index this thread users go here and redirected to closed thread to WEB-1647 where just right now someone add a comment probably without reading all comments  🙂

Edit: I confirm that What is just commented in WEB-1647 by Yves Peissard - now when i want to create second account with the same my own domain, that i just recently create account and buy a copy, that now i was not able to do that with the same bug appears "IllegalArgumentException: Registration failed".

Hi, I am still experiencing the "Invalid Registration Error" (IllegalArgumentException: Registration failed) when trying to register for a new Mojang account using a custom smtp domain. I've tested with a non-existent Gmail account and it works fine.

I am having the same issue. I have a many-years old account using my personal domain and I created another mojang account on that domain last year for one of my children.  But now I go to create a new account and buy a copy for another family member and I get "IllegalArgumentException: Registration failed". 

Update: As of 6/7/20 I was finally able to create an account with the custom domain in question.

Running into this issue again with at least '@outlook' addresses 

Still occurring with custom .me domain on May 30, 2020 at 1:39 Pacific (-07:00)

Same problem with own .nl domain name on June 3, 2020 at 9:14 CET +1

Update June 15, 2020: Over the weekend I was able to create more accounts for my kids so they can play together simultaneously on a Minecraft server (my reason for multiple accounts on my domain). I found that if I typed the password in by hand instead of pasting it from a password manager, I had a better chance of getting the captcha and creating the account. But I still received the error message more times than an account was created.

Update June 12, 2020: Today I was able to create one additional account with an email address using my custom domain but now cannot add another. Same error as below.

As of June 8, 2020, when trying to register a new Mojang account at https://my.minecraft.net/en-us/store/minecraft/#register with a custom domain, I am receiving the following error:

"INVALID REGISTRATION

Please go back and double check your information and make sure that it is valid.

IllegalArgumentException: Registration failed."

I already have two accounts registered to the custom domain and it seems that I cannot create anymore. As I use the custom domain for my family and it services our primary email addresses, I'd like to be able to create more accounts with that domain name. My domain name type is a .net.

I am having this same issue for my custom domain.  I get an "IllegalArgumentException: Registration failed." when attempting to register under an @oru.edu address.