[jeroenhd]

Samsung is particularly annoying about this. You can't sign up for an account with "Samsung" in the user portion. They'll straight up block [e-mail], so I've resorted to misspelling their name in the email address and they seem perfectly fine with that.

[sidharthv]

I've been using sam.sung@domain for them. First time I've come across this block in years of using this method.