Email not working when domain is hosted with external provider

[Erniedb]

Im currently running a trail of plex to see if it meets our requirements.
My domains are currently being hosted by an external provider and I have made the dns entry to point it the the server running plesk.
Now we can access the site created through plesk but the emails are not working not the webmail or even trying to forward the mails.

Please advice as everything else regarding plesk meets our requirements.

 

[kpmedia]

1. Did you ensure all records (A, MX, others) were changed in DNS?
2. Are you sure that the email service is working correctly? Did you telnet in and try to send anything?