exim4 and HELO

[Brian Walker <bfwalker@netvigator.com>]

Greetings,

playing around with installing exim4 for mutt 1.5, I am unable to find 
out how to rectify this problem:

exim4 -v abc@def

the output includes the error message:
SMTP<< EHLO
SMTP<< 501 5.0.0 EHLO requires domain address

in /etc/hostname I have tried various addresses including localhost and 
127.0.0.1

the exim4 config mentions EHLO once - uncommented the script, no effect 
on output.

Where do I make the change/add a domain address to please HELO/EHLO?

Many thanks

Brian