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Improving Email Deliverability with Marketo – from The Inside Out


Any email marketer or business owner worth their salt would be disconcerted by the following scenarios:

Those are the all-too-certain signs of a deliverability fiasco. If you are yet to see these signs, good for you. But you don’t want to play fast and loose with email deliverability. Poor deliverability may translate into a major revenue drain. 

Consequently, your goal as a marketer should be to improve email deliverability. One of the best tools out there to help you do it is Marketo. Let’s explore how Marketo can help you improve deliverability. (You can also contact our Marketo-certified specialists and enhance your email campaigns.)

1. Advanced Email Deliverability Features

Marketo’s advanced deliverability features allow you to:

2. Dedicated, Trusted, And Shared IPs

Marketo offers three IP options: dedicated, shared, and trusted. Let’s take a look at each of these in brief. 

3. Marketo Feedback Loops

If a user marks your email as spam, the sender will be automatically notified. That’s what a feedback loop, in a nutshell, is. 

When a recipient marks one of your emails as spam, the Internet Service Provider (ISP) notifies Marketo instantly, following which Marketo unsubscribes the recipient under “Customer Complaint Received from ISP.” The complaint is then taken up by Marketo’s Email Compliance System. Marketo has dedicated feedback loops with the following email providers:

In their documentation, Marketo has specified that and (Russian and Chinese IPs, respectively) cannot be set up for a customer on Trusted IPs and Shared IPs. 

4. Marketo’s Bounce Handling

Being an advanced email system, Marketo is equipped to distinguish between a hard bounce and a soft bounce in accordance with a wide range of bounce codes. 

Typically, 400 error codes signify soft bounces (temporary failures), whereas 500 error codes signify hard bounces (permanent failures). You can view the list of bounce codes that Marketo manages right here

Marketo uses the following fields to categorize bounces:

Note that you will not be able to view bounce data without first creating an Email Performance Report on Marketo. 

Marketo recommends creating a directory of leads bouncing emails in order to better understand different bounce scenarios and accordingly take preventive measures. You can build the directory following these four steps:

  1. First, create six custom fields divided into two DateTime fields, two Score fields, and two String fields. 
  2. Next, create a program to store everything and name it ‘Directory of Leads Bouncing Emails.’
  3. Then, create a static list. The static list will contain all the leads that are currently bouncing emails back to you. You can call it ‘Active Bounce List.’
  4. Create two Smart campaigns to add and remove leads from the Active Bounce List. Briefly, the first Smart campaign will look for any bounces that might happen over time. The second Smart campaign will flush out leads from your list after successful re-deliveries. 

5. Branded Return Paths

A good return-path address will boost your email deliverability. Since return-path is an SMTP address, it is used by email servers to determine how best to filter your messages. 

Now, some email networks look for branded return-paths. In other words, when the From domain is associated with your brand, rather than with the email system you are using, it can improve deliverability. 

And guess what? You can set up branded return-paths within Marketo. What’s more, customers on both Dedicated and Shared or Trusted IPs can avail of this feature. Marketo’s default return-path domains include the following:

By way of illustration, here’s how the Standard and Branded instances will look like:

6. Configuring Authentication Protocols

Marketo allows you to configure authentication protocols such as DKIM (Domain Key Identified Mail), SPF (Sender Protection Framework), and DMARC (Domain-based Message Authentication, Reporting, and Conformance), You can view how to configure these in Marketo right here

N.B. If you are using Marketo to send test emails, you need to add Marketo to your allowlist in order to circumvent anti-spam vendors. Marketo recommends that you add the following IP addresses to your allowlist:

As we explained in the previous section, some email networks tend to favor branded return-paths. The same holds true for test emails as well. Not all anti-spam vendors use the IP addresses for allowlisting. In those cases, Marketo recommends allowlisting ‘*’. 

Now, apart from inbound SMTP, which accepts emails only from domains hosted by the user, Marketo Engages employs outbound SMTP, which can send emails to any random domain. If your organization uses allowlisting to block access to certain servers, make sure that Marketo Engage IP address blocks are added to the allowlist. 

Here is the list of Marketo Engage IP address blocks that make outbound calls:

The following list shows individual IP addresses that make outbound calls. 

Wrapping Up!

Deliverability can either make or break your email campaign. In fact, without good deliverability, there is no point in doing email marketing since your contacts will not be able to view your emails. 

Where reputation and revenue are concerned, you don’t want to take any chances. Look out always for signs of deliverability issues so that you can forestall a major escalation. More often than not, it helps to keep an external deliverability consultant standing by, instead of just relying on an in-house deliverability expert. 

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