"No such account. Sign up Now" message although e mail has been created

"No such account. Sign up Now" message although e mail has been created

Hello.
I created a new free account for ppastucturals.gr. I initially used the e mail ppastructurals.gr@webgalaxy.gr to sign up. 

After setting up the account (mx records etc), I created the users
info@ppastucturals.gr
pp@ppastucturals.gr
ds@ppastucturals.gr
np@ppastucturals.gr
bk@ppastucturals.gr
However when I try to login with these e mails at https://www.zoho.com/mail/login.html,
I get "No such account. Sign up Now".

I can only login using ppastructurals.gr@webgalaxy.gr
and I can send and receive e mails at info@ppastucturals.gr when login that way.

What am I doing wrong?
Thank you