Sentora and 1and1: emails keep disappearing

I have a server with Sentora installed on CentOS 6 and a domain (let's say mydomain.com) bought from 1and1.

Here are the settings I made in 1and1 web interface:

Name Server Settings
Name servers:
(*) 1&1 name servers
( ) Other name servers

A/AAAA and CNAME Records
IP address (A Record):
( ) 1&1 IP address
(*) Other IP address
IPv4 Address 111.222.33.44
IPv6 Address (empty)

MX Records
Mail Exchanger (MX Record):
( ) 1&1 mail server
(*) Other mail server
MX1 mail.mydomain.com Priority 10
MX2
MX3
MX4

TXT and SRV Records
(none)

In Sentora I made a mailbox
I sent an email from my other mailbox to , it did not arrive nor I received an error response from the server.
And the other way round, mails from to are silently dropped too.

Also while I can see target mail.mydomain.com in Domain Management / DNS Manager I cannot resolve mail.mydomain.com.

What did I do wrong and how to fix it?

 

Is there actually a mail-server running on your host?

 

I believe so. If you let me know the command line to verify that i will do.

 

Anyone?