Volume-based filtering may be pre-sorting your marketing messages to the bulk folder or worse.

You've got a great product, fantastic customer service, and a loyal base of customers that opt-in to your email list. They're interested in staying abreast of new products, special offers, and other news and relevant information you send them.

Unfortunately, customers don't seem to be getting the message - literally. You are careful to avoid phrasing and formatting mistakes that might confuse your permission-based marketing message with the scourge of unwanted junk.

However, depending on the size of your email list, and how your email software service handles delivery, the volume-based filters that Internet Service Providers (ISPs) use to sort the good from the bad may be frustrating your efforts.

In the audio book, "Sound Advice on Email Marketing," author Peter McCormick explains that "since most spammers attempt to send hundreds or thousands of emails through a single ISP, volume filters attempt to detect incoming spam by monitoring the number of simultaneous connections a mailer is attempting to make."

"If too many connections are made at the same time," says McCormick, "the ISP will block the email or send it to the bulk folder," and never reach the customer actually wanting to receive it. He also reminds marketers to practice good list management, saying that too many bad addresses - combined with volume management mistakes - can trigger the filter.

How does a marketer avoid volume filtering? "Marketers can ensure their mail is being delivered to its intended audience by selecting an email service or software that provides the ability to monitor and adjust volumes by ISP," says McCormick.

Peter McCormick offers advice on email marketing strategies each week in the free audio newsletter from What's Working in Biz, http://www.whatsworking.biz/full_story.asp?ArtID=92