It is possible to host websites in a shared hosting environment and provide your customers the option of using a 3rd party email provider for their email services right?

I am setting up a company hosting sites in a shared hosting server but would like to use netnation to host their emails with the same domain name.

Thanks.

It's certainly possible if you have DNS control or you can get your customers to point the MX records at the third party servers. I don't know off hand of third party email providers apart from Gmail. In this case however the domain owner should sign up for this service I think...

I think many companies offer email hosting.

Some are:
http://www.bluetie.com/
Yahooo Business email service
netnation.com

I'd like to use netnation myself.

Yes I think the customer will have to pick a email provider and sign up themselves.

Yes it is possible by editing the MX records for the domains. I've been using the Gmail service with my e-mail for a while now and it is working perfect. I also set up that for my clients, should they so wish.

You can also try www.mail2world.com and www.webmail.us

Good luck :)

Runbox! I don't use them any more, but I used them for close to a year and they were pretty good.