I have what is to me an unusual situation.

I have a client for whom I have built a website which I will be hosting, they have been using their domain name for their email addresses for a long period before I came along so moving their email account to my host would be problematic and building the website with their current host would also be problematic because their host is very restrictive.

So to fix this I altered the A record in their existing control panel to point the domain name to my server. As a result I can see the pages that I have created at their domain and they can still access their existing webmail. However, it appears that they are now experiencing problems receiving email so I can only assume my solution was incorrect.

What is the correct way to point their domain at my website but keep their webmail with the existing host?

EDIT: 25/5/2012 - My client has finally responded to me after changing the MX record on their existing C-Panel. Email to their email address were being bounced back with the error 'no such recipient', so I set up the same email address in the new C-Panel and changed the MX record there to 'Remote mail exchanger' which has stopped the emails bouncing but has apparently lost them in cyperspace! Unfortunately I can't add a new record because this would require a fully qualified domain name and their domain name is of course pointed at our server!