Return Path's Ken Takahashi is often asked by email marketers which ESP is the best at deliverability.
The good news: when it comes to infrastructure and the basic technological and authentication set ups that ISPs are looking for, all the major vendors in the United States do just fine. Additionally many top-tier vendors have ISP relations or other deliverability professionals who can help fix minor problems as they arise. The smaller players tend to manage this through their technology departments and others offer that service through outsourcing.
But, here's the bad news: No ESP has the magical power to get your email to the inbox. And the truth is that four of the five root causes of deliverability problems are wholly in your control. These are complaints, unknown users, spam traps and content - which are all associated with your email practices and policies.
Weak permission, irrelevant content and poor hygiene practices can't be fixed by anyone but your team. In fact, many of these problems begin with your data collection practices, a point long before your ESP is involved with your program. The fifth cause, infrastructure, is the only part that the ESP has direct influence over.
Moreover, fixing problems caused by complaints, unknown users, spam traps and content is beyond the scope of most ESPs. In the case where an ESP can handle this for you, this is typically accomplished through their consulting divisions. As this is above and beyond what their deliverability team can handle, you should expect to be charged separately for these services. If an ESP states that this service is included, they usually mean their reactive monitoring and relationship services. An intense, high-level consulting project into your email program aimed at resolving root causes for deliverability simply can't be accommodated within their traditional CPM model.
The bottom line is that all vendors have the infrastructure to get your email delivered. So you can relax – if you have a great reputation you aren't going to inadvertently pick an ESP that will ruin your deliverability. But, if your reputation is an issue and your email isn't getting through, you need to be prepared to pay more -- to the ESP or to someone else -- to improve your program and increase your inbox delivery rate.
Source: Return Path