What This Feature Does
The MX Based Segments add-on lets you group contacts by the backend email provider they use, such as Google Workspace (Gmail), Microsoft 365 (Outlook), or Yahoo. It does this by reading the MX (Mail Exchange) records of each contact's email domain, which tells SendX exactly which mail server handles that address.
Because checking public DNS records takes processing power, you must manually scan your contacts before you can segment them. Once scanned, you can use these segments to diagnose and resolve deliverability issues much faster.
When to Use This
If your open rates drop after a campaign, this feature helps you figure out whether the problem is isolated to one provider or happening across the board. A Gmail-specific dip points you in a very different direction than a platform-wide issue.
You will get the most out of MX Based Segments when you want to:
Investigate low open or click rates by checking whether a specific provider is underperforming.
Confirm whether contacts are landing in spam with a particular provider after a deliverability dip.
Run a targeted test send to one specific provider before drawing conclusions about your broader list.
Keep an eye on inbox performance across major providers on an ongoing basis.
Step 1: Enable the Add-on and Scan Your Contacts
Before you can build an MX segment, you must turn the feature on and instruct SendX to analyze your list.
Go to Settings from the main left-hand navigation.
Open the Add-ons section.
Scroll down to find MX Based Segments and toggle it ON.
Click directly on the add-on to open its dashboard.
Navigate to the Settings tab within the add-on. Here, you will see a breakdown of your contacts:
Scanned Contacts: Addresses that SendX has already analyzed and categorized by provider.
Unscanned Contacts: New or unanalyzed addresses that do not yet have MX data attached to them.
Click the Scan Contacts button located in this Settings tab to process your Unscanned list.
Crucial Step: You must wait for the scan to complete before moving to Step 2. If you build a segment using Unscanned contacts, the segment will be empty.
Step 2: Create a Segment by Email Provider
Once your contacts are successfully scanned, the email provider filter will become available inside your segment builder.
Go to Segments from the main navigation.
Click Create New Segment, or open an existing one to edit it.
In the segment conditions, select Email Provider as your filter.
Choose the provider you want to target from the dropdown (e.g., select Gmail to segment all contacts whose email is hosted on Google's servers).
To include more than one provider in the same segment, simply add multiple selections (e.g., build a segment that covers both Gmail and Outlook contacts at once).
Click Save.
SendX will instantly populate the segment with your Scanned contacts whose email domains match the MX records for the providers you selected.
Using Provider Segments to Investigate Deliverability
Once your segments are set up, here is how to put them to work:
Compare performance by provider: When reviewing campaign results, filter your reporting by a provider segment to see open rates, click rates, and bounces for that group specifically. If Gmail contacts are significantly underperforming compared to Yahoo or Outlook, that tells you exactly where to focus your troubleshooting.
Send targeted test campaigns: You can send a campaign exclusively to a provider segment. This is highly useful when you want to confirm whether a spam placement issue is consistent with a specific provider before taking any drastic action.
Cross-reference with deliverability alerts: If SendX surfaces a deliverability warning, pull up your provider segments first. Identifying the affected provider early narrows down the root cause—whether that is a domain reputation issue, a content flag, or a sending frequency problem.
Important Notes and Best Practices
New Imports are Unscanned: This scanning is not an automated background process. Whenever you import a new batch of contacts into SendX, they will initially be marked as Unscanned. You must return to the MX Based Segments add-on's Settings tab and click Scan Contacts again to categorize those new subscribers.
Layering Conditions: MX Based Segments can be combined with other conditions—such as engagement status, tags, or custom fields—to build highly targeted groups (e.g., Gmail users who haven't opened an email in 90 days).
No Data Modification: This feature does not modify or alter your contacts in any way. It only reads public provider information to group them.
No Limits: There is no limit to how many provider-based segments you can create.
Frequently Asked Questions
Why is my newly created MX segment empty?
This usually means your contacts are still Unscanned. Go to Settings > Add-ons > MX Based Segments, open the Settings tab, and check your Unscanned count. Click Scan Contacts to process them, then check your segment again.
Can I target multiple providers in one segment? Yes. When setting the email provider condition, you can select more than one provider. The segment will include contacts from any of the providers you choose.
The Email Provider filter isn't showing up in my segment builder. What should I do? This usually means the add-on hasn't been enabled yet. Go to Settings > Add-ons and make sure MX Based Segments is toggled ON. If it is already enabled and the filter still isn't showing, try refreshing the page.
Does this work for custom business email addresses (B2B)? Yes! As long as the contact's email domain has publicly available MX records, SendX can read them. For example, if a business uses Google Workspace for their corporate email, an address like name@corporatebrand.com will correctly be identified and segmented under "Gmail."
Is there a cost to use this? No. MX Based Segments is completely free on all SendX plans.