Navigate to the "Lists & subscribers" tab in the Campaign Monitor sub-navigation bar, then click the list in which you want to create or modify segments.

Then choose "Segments" from the menu on the left hand side

From the Segments page, click on "Create a new segment"

Create the first rule to define your segment - you can use any subscriber details or custom fields as the basis for your rule.

Use a condition (1) to set up your rule and enter the field value (2) you need to complete the rule.

Once you have your first rule set up, you can use the "AND" (1) and "OR" (2) functions to add additional rules to further define your population.

Using the "OR" function widens your segment population so your final segment will be larger because contacts can match to either criteria listed.

Using the "AND" function narrows your segment population so your final segment will be smaller because contact must both criteria listed.

When you're satisfied with your rules, give your segment a name  (3) and click "Save and preview".

Always check your segment to ensure it includes only the people you want it to include. A good first step is to look at the total number of subscribers (1) - is that a reasonable number based on what you know about the segment of your list that you're aiming to define?

You can also export the entire segment (2) as a csv file to check more fully that the segment is the entire population you're trying to define and no one else. Note that the subscribers you can see in the page view in Campaign Monitor are just a preview of all subscribers. If you need to check if a specific person is included in your segment, you can type their name into the search bar (3).

You can always adjust your existing segments by adding or removing rules. Delete rules by clicking on the trashcan icon on the right side of the page. Add additional rules by clicking on the "AND" or "OR" functions and defining a new rule. To change the name of your segment, click "Edit name".

After you make changes, be sure to spot check your subscriber list to ensure you have the correct group.

You can use segments as the list of subscribers you'll send an email to and you can also create specific content blocks in your emails for different subscriber groups and use segments to determine which of your subscribers should get which content blocks.