Pretty much all email systems except Exchange use SMTP to accept email from clients.
You'll want to find the SMTP server IP for the ISP you're connected through, and enter that - for example, if the internet connection is through Comcast Cable, you'd want to use Comcast's SMTP server.
my ISP is orange.
according to this
website the smtp server is smtp.orangehome.co.uk. if i trace that in CMD i get the ip: 184.108.40.206 will this be the ip to use?
Correct, that SHOULD work.
what about the port and 'local email address'?
Port is 25, unless your ISP specifies otherwise.
Local address would normally be your address, although it can probably be just about anything. You should probably enter something at least resembling a real email address, as the SMTP server may reject it otherwise.
normally you would enter the smtp server name, eg. smtp.orangehome.co.uk
You can also use the IP if you want, once its not dynamic (rare).
He HAS to use the IP - the DVR setup doesn't give the option to enter a hostname (see screenshot above).