MailBox Error 550

[sento]

Hey i hav the following problem.
When is sent a mail to my mail server i get a mail back from postmaster with a Diagnostic code: smtp;550 5.1.1 
But sending mails from roundcube works fine and without problems.
What might i have done wrong? 
I have CentOS 6.7 and the newest sentora 1.0.3

[Me.B]

1. Check DNS and MX are correctly configured.

2. When you send email, how ? PHP ? Outlook? using wich SMTP?

M B

[sento]

1. Check DNS and MX are correctly configured.

2. When you send email, how ? PHP ? Outlook? using wich SMTP?

M B

I guess there is the problem i didn't do it right :/
Here i changed right now at godaddy the mx record to mail.kkip.de
http://prntscr.com/a7jt6s

Do i have to change anything else there, like cname or by mx smtp.secureserver.net?

And here the DNS and MX settings in Sentora, and i forgot to mention i have two domains main is kkip.de and secondary mhutmacher.com
kkip.de
DNS http://prntscr.com/a7jodj
MX http://prntscr.com/a7johw
mhutmacher.com
DNS http://prntscr.com/a7jnsc
MX : http://prntscr.com/a7jnzw

2. When i send a email from what to where?
When I send from mail@kkip.de, i use Roundcube which should be PHP ?
When I send to mail@kkip.de then with the standard Mail client  from OS X, so SMTP i guess.


Thank you for your fast response Me.B