In this article, Bill Nussey explains that there are steps B2B marketers can take to ensure more of their messages get through to the people who have asked for them.
As long as you are already sending permission-based, well-branded messages, promptly honoring unsubscribe requests and scrubbing bounces from your lists, these six tips can help improve your B2B email deliverability:

1. Check blacklists

According to MarketingSherpa’s "Email Marketing Benchmark Guide, 2007," most email marketers check whether they are on a blacklist less than once a month, and yet more than a third of the corporations use them in their anti-spam efforts.

2. Look into an email reputation service

Email reputation services such as Sender Score and Habeas compile detailed information in order to categorize senders based on their email reputation, and then they vouch for companies with the best reputations. Such endorsements may help you get through some corporate firewalls.

3. Use a deliverability provider

Companies like Pivotal Veracity or Return Path can help you get a handle on your reputation by auditing your emails to determine why they aren’t being delivered. These audits uncover causes and fixes for content and coding errors, rendering problems, "black-holing" (messages that are discarded by ISPs without notice), and other factors affecting your reputation and deliverability.

4. Get authenticated

The three major authentication standards are Sender Policy Framework,
Sender ID and DomainKeys. They have all been adopted by virtually every
major ISP, so if you haven’t already done so, be sure to implement all
three schemes in your email program.

5. Consider a double opt-in

One way to ensure better deliverability is by using a process called
double opt-in, which requires registrants to confirm their desire to
receive your messages by clicking a link in an email. If they don’t
respond, they are not added to your list, and you can assume your
message either got caught in a spam filter or that the person is no
longer interested. However, this technique has a high drop-off rate; as
many as half of all those who originally register fail to follow
through with a confirmation.

6. Tell recipients to expect your message

Whether you use a double opt-in or simply follow up registration with a
confirmation or welcome message, be sure to let recipients know with
the opt-in that your message will arrive shortly, and then send it
right away while they are thinking about you. In your message, ask recipients to add you to their email address book to ensure that they continue to receive your emails.

As you focus on these areas, don’t forget to measure the results of any
changes you make in order to understand what changes work best for
deliverability to your B2B email list. Taking steps to protect your
email deliverability will pay huge dividends in the future.

Source: iMedia Connection