This is a must-read if you are emailing to BellSouth addresses. Just this week, we at MarketingSherpa learned that around 400 of our newsletter subscribers who use BellSouth haven’t been getting our emails. This problem is almost certainly affecting any other marketer emailing to BellSouth names (i.e., probably you).

Evidently, BellSouth modified its filtering system in January 2007. The modification appears to stop some or all mass-broadcast email in HTML format, according to email service provider ExactTarget, which has been researching this project for multiple clients.

MarketingSherpa tested other methods and determined that text-only emails are delivered. Please note: this does not mean multipart MIME and it does not mean look-alike text. It means text only.

We strongly suggest you start using text-only email for BellSouth names. The incident only underscores our ongoing advice that you monitor your email responses by ISP. If you are unable to spot ISP-specific problems, you can't fix them. It also means that if email is important to your company, you need to be able to segment your list by ISP on ocassion and format it to get your mail through. Check with your email service provider.

Marketers who have geographically segmented files should know that BellSouth provides Internet service in the following states: Alabama, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, South Carolina and Tennessee.

While BellSouth was recently acquired by AT&T, no indication has been made whether one of their email systems will umbrella customers for both brands. However, with AT&T’s reach in critical markets such as San Francisco/Oakland, it’s worth keeping a close eye on -- just in case the BellSouth filter all of the sudden becomes the company standard.

For a quick overview of how different ISPs and B-to-B organizations filter email differently, check out these two charts from recent MarketingSherpa research:
Click here for charts
(To make the charts larger, just click on the image.)