Could someone (Sebastian?) elaborate or send some learning materials/links on this concept of relaying as I'm running out of patience with the arvixe people  where I'm being hosted at as their server seems not to have such capacity?

Occasionally when sending emails from my DNN 7.4 portal the emails bounce back as undelivered with ff. info:
________________________________________________________________________________________________

This is the mail system at host relay.mailchannels.net.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                   The mail system

<recipient.email.address.here>: host recipientdomain.net[recipient IP address here] said: 451
    GL - temporary problem. Please try again later. (in reply to DATA command)

Reporting-MTA: dns; relay.mailchannels.net
X-Postfix-Queue-ID: 5F90F52EB
X-Postfix-Sender: rfc822; myaddresshere@mydomain.net
Arrival-Date: Fri, 27 Mar 2015 15:36:19 +0000 (UTC)

Final-Recipient: rfc822; recipient.email.address.here
Original-Recipient: rfc822;recipient.email.address.here
Action: failed
Status: 4.0.0
Remote-MTA: dns; recipientdomain.net
Diagnostic-Code: smtp; 451 GL - temporary problem. Please try again later.
________________________________________________________________________________________________
Interestingly my emails to above recipient (and others) apparently get delivered sometimes but at other occasions they do not. And when they don't I don't always receive "the undelivered mail" message.
This idea of relaying is mentioned in this thread here.
Funny though the problems started only when I moved to arvixe. So the logic is they are missing something.

Any elaboration on this is welcome as the arvixe people say everything is ok at their end and my system (meaning DNN) is to be blamed. 

Chase,

Do you have by any chance a localized website in DNN? Which version are you on?