In our Digital Marketing Technology technology evaluations, we spend a fair bit of time on the topic of email "deliverability," comparing and contrasting different vendors on how they approach the challenge.
To be sure, deliverability is a multi-dimensional challenge: you have to pay attention to myriad details ranging from message subject, headings, and content, to how you're going to approach the particular filters set up by the likes of AOL and Google, to everything in-between. Some people assume this is a high-end problem, only affecting large B2C marketers.
That's not the case. In fact, there's one particular gotcha here that we find afflicting higher-brow B2B marketers. Sometimes companies with the kind of smaller lists you see in the B2B world turn to lower-end marketing automation services in the absence of intense scalability requirements. And sometimes that does not turn out well.
You see, those B2B enterprises may find themselves sharing infrastructure at that vendor with mom-and-pop outfits who might not be too conscientious about where they got their lists and how they market to them. Those marketing automation vendors, and their IP addresses, start to get a bad rap. Some negative reputations are short-term; others are more lasting. The point is, you can get labled as untrustworthy just because you live in a high-crime neighborhood. Your messages have a higher likelihood of ending up labeled spam or zapped altogether -- by an ISP, at the firewall, or in the desktop client.
Of course there are various things you can do to mitigate this, not the least of which is paying for a dedicated IP address. But that may not completely resolve the problem, as you may face delays "warming up" an IP address, and you may need a higher volume of messages than you would ordinarily send to keep it legit. Finally, even a dedicated IP may not completely remove the stigma of your law-shirking neighbors.
There are other ways to help yourself here that require getting into the arcana of how modern networks operate, how messages get routed, and domain names validated. But that's just my point: it's not a simple challenge. So my advice is, get smart about the issue and carefully research your options before signing contracts.