Yes, good advice above.
I see the most difficulty in selling domains as in other profession, is the skill set required - No offence intended but those with a code-building mind-set are not always the best adapt at working successfully in a sales environment. Of course there are exceptions but those few tend to be at the very pinnacle of their game.
In most sales environments, it's gaining that inital flash of interest thats the door opener, Most company decision makers are overwhelmed by information overload and trust me they know/learnt how to filter out superfluous material.
If you want one single best bit of advice make sure you put your best effort into that one-line in the subject header - and for sales (dosen't apply to buying) Don't expect to be taken seriously if your using a free email service. and thats if you get past the email filters.