A written version of this guide can be found here:
You can point email towards an external mail server by changing the MX records of the domain name within the Advanced DNS section of your control panel.
When pointing your domain name towards an external mail platform, your email supplier will provide you with an MX record. This will look similar to the following: aspmx.l.google.com .
Difficulty: Intermediate (Knowledge of DNS required)
How long will it take me?
◾Around 3 minutes
◾The changes may take several hours to propagate.
What will I need?
◾Your control panel username and password.
◾A domain name registered with Fasthosts, or using Fasthosts nameservers.
◾The MX records of your email service provider.
Publisher: Fasthosts Internet
You can watch this video also at the source.