It has been shown that humans can learn to filter out repetitive visual or audial noise. One study on a particularly common billboard showed that very few people who saw it remembered seeing it, versus recall of more rare ones. I think the same applies to frequent emails. I won’t say “spam” because I’m talking about legitimate senders, such as a company you’ve actually bought things from or a department in your company that sometimes has something interesting to say.
My work and personal email systems have easy-to-use filtering machanisms, such as “ignore”, “spam”, “junk”, or rules that send emails with a certain topic or sender to a folder. And I love to use them! If you want my attention, your goal is to find the optimum rate of message delivery at which I will listen to your message without pressing the spam/junk button or habitually blocking it out.
Companies that I’ve bought a product from one or twice, but then send me emails almost every day are so obviously annoying I enjoy setting up a filter to eliminate them. There’s a lesser rate, say once a month, where I wouldn’t bother to filter them and might even scan the subject line.
Maybe a good idea is to start out with more frequent marketing messages right after a purchase, but if there are no repeat purchases after a certain time (like 30 days), ratchet back the frequency. My optimum level may be to receive 3 marketing emails per year for every purchase I make that year. Go beyond my tolerance and you’ll probably find yourself on my spam list.
The same applies within the firewall. Even a big boss with formal authority will get mentally filtered out if she sends lots of short emails that aren’t actionable. Putting some of those messages in a “VP’s blog” and bundling the rest for sending in a monthly newsletter may be more likely to meet the VP’s communication goals. An internal social network page would be another pull-based mechanism to avoid desensitizing employees to the messages being pushed at them. By caring about the attentional drain on the recipient of her messages, the VP would be in a better position to get her most important messages across.
In email, as in life, speak less if you want to be heard.