Eventually with the help of support at both Hostgator and Go Daddy, a solution was reached. As it caused me a degree of stress and frustration, I thought I would share this solution with you. So this is what you do:
- Log into Go Daddy and navigate to the Total DNS Control Panel
- Look down the C Name table and delete the "mail" entry.
- Add a new A Record - use "mail.domainname.com" (where "domainname.com" is the domain name you are using - so with my website it was "mail.fenlandtextilestudio.co.uk"). Point this to the IP address that Hostgator gave you when you first signed up.
- Now go to the MX (mail exchange records) and delete the existing records.
- Finally, set the MX record to "mail.domainname.com" (where domainname.com is your domain name).
I hope this is useful and works for you if you need it. Feel free to leave a comment if you have any problems and I will do my best to assist. Don't worry about changing the settings for your domain name - if it all goes horribly wrong you can reset to the default values!