First impressions are everything and an unwanted or uninvited email may not be the trick you are looking for. It's tempting to dismiss snail mail as slow and costly. While electronic mail can be instantly dismissed as junk mail and deleted, a letter sent by the postal service leaves the impression that the sender placed enough importance on the content to sit down and write, stamp and mail the letter. Beyond that, when your audience doesn't have time to read the letter immediately, they may leave it on the desk to be read later. A letter sitting on a desk may not seem like much, but if your reader scans the letter quickly and finds it interesting, it may be read again.
Paper sits around and is often read and later reread.
If the content of your letter is interesting enough, it may be discussed or mentioned at lunch, during a meeting or even in passing. We think of paper mail as a kind of mental cue. Something lies around in the subconscious until an idea hits you. This is where your own research and knowledge of your target market come in. Once you know which companies you want to write to, you'll need to find the appropriate email or postal address.