Step by step guide to importing and segmenting contacts in Mailscale

If you’re staring down a messy spreadsheet or a stack of email lists and wondering how to get them organized in Mailscale, this guide is for you. Whether you’re new to email marketing tools or just switching platforms, I’ll walk you through importing your contacts and actually making sense of them—without hand-waving or magical thinking.

Before You Start: What You’ll Need

Let’s not overcomplicate things. Here’s what you should have ready:

A clean(ish) list of contacts in CSV or XLSX format. If it’s messy, don’t sweat it—just know you’ll have to do some cleanup.
Access to Mailscale (if not, go get set up here).
A rough idea of how you want to segment your audience (think: customers vs. leads, regions, interests).

If you’re missing any of these, take five minutes to round them up. Winging it halfway through is how you end up with a Frankenstein’s monster of a contact list.

Step 1: Prep Your Contact List

Why Bother With Cleanup?

Garbage in, garbage out. If your list is full of duplicates, typos, or people who never signed up, your campaigns will flop—or worse, get marked as spam. Spend a little time here, and you’ll save yourself headaches later.

Quick Cleanup Checklist

Remove duplicates: Sort by email and delete repeated rows.
Check for required fields: At minimum, you’ll need an email address. Add first/last names if you want to personalize.
Standardize columns: Use simple headers like email, first_name, last_name, company, etc.
Watch for weird formatting: Extra spaces, strange characters, or broken rows are common culprits.

Pro Tip: If you’re merging lists from different sources, keep a column noting the source. It’ll help with segmenting later.

Step 2: Import Contacts Into Mailscale

Time to put your list into the system.

How to Import

Log in to Mailscale.
Go to the “Contacts” section.
Click “Import Contacts” or the upload button.
If you don’t see it, you’re probably on the wrong tab—look for something like “Manage Contacts.”
Upload your file (CSV or XLSX).
Map your columns.
Mailscale will guess, but double-check. Make sure email is mapped to the right field and so on.
Choose how to handle duplicates.
You’ll usually see options like “skip,” “update,” or “add as new.” Updating is safest if you’re refreshing existing contacts, but don’t be afraid to skip if you’re unsure.
Start the import and wait for confirmation.
Big lists can take a few minutes. Don’t refresh like a maniac.

What If You Mess Up?

Don’t panic. Mailscale won’t overwrite everything unless you tell it to. If you upload the wrong file, just delete the list and start over. There’s no “one big undo” button, but you won’t break anything just by importing.

Step 3: Check for Errors and Clean Up

Even if you prepped well, imports can spit out errors.

Review the import summary. Mailscale should flag any rows it couldn’t process.
Fix and re-upload problem contacts. Usually, it’s missing emails or bad formatting.
Spot-check a few records. Open a handful of contacts and make sure names, emails, and custom fields look right.

Pro Tip: If you see a ton of errors, it’s probably a formatting issue. Open your file in Excel or Google Sheets, save as CSV, and try again. Sometimes Mailscale chokes on “fancy” Excel files.

Step 4: Segment Your Contacts (The Smart Way)

Why Segment?

This is where most folks get lost. Segmenting isn’t just about making a bunch of lists—it’s about sending the right message to the right people. The trick is not to overthink it. Start simple.

How to Segment in Mailscale

Go to the “Segments” or “Lists” section.
Click “Create Segment” or “New List.”
Set rules based on your fields.
For example: “Country is United States,” or “Source contains Webinar.”
Give it a clear name. Don’t get cute—future you will thank you.
Save the segment.

Segment Ideas That Actually Work

Customer vs. Lead: If you’ve got a “status” or “type” column, split on that.
By Interest or Product: Use tags or custom fields if you have them.
Engagement Level: If you’ve got data on who’s opened your last few emails, filter for active vs. inactive.

What Not to Bother With (At First)

Dozens of micro-segments: If you’re just starting out, don’t try to create a list for every possible scenario. You’ll just confuse yourself.
Demographic data you don’t have: Don’t try to split by age or job title unless your data is actually there—and accurate.

Step 5: Tagging and Custom Fields

Tags and custom fields are how you get more granular—without making 50 different lists.

When to Use Tags

Events: Tag all contacts from “Spring 2024 Webinar.”
VIPs or Key Accounts: Tag them so you can always filter them out (or in).
Opt-in Preferences: If you’re collecting info on what people want to hear about, tags are your friend.

How to Add Tags in Mailscale

Bulk add during import: If you have a “tags” column, Mailscale should pick it up.
Manually: Select contacts and add tags from the action menu.
Automatically: Set up automation rules (if you’re feeling advanced).

Custom Fields

If you’re tracking data that doesn’t fit the standard options (birthday, renewal date, favorite color—hey, I don’t judge), set up a custom field before you import. Otherwise, that info goes nowhere.

Pro Tip: Only create custom fields you’ll actually use. More fields mean more ways for your data to get messy.

Step 6: Keep Your Lists Healthy

Don’t just set it and forget it. Bad data creeps in over time.

Regular Maintenance

Remove bounced or unsubscribed contacts at least monthly.
Check for duplicates if you’re importing from multiple sources regularly.
Revisit your segments every few months—if you’re not using one, archive or delete it.

Pitfalls to Avoid

Letting old lists sit forever: Outdated contacts hurt deliverability.
Over-segmenting: More lists = more confusion (and more mistakes).
Ignoring errors: Fix import errors right away, or they’ll pile up.

Step 7: Test Before You Hit Send

Don’t trust your own work blindly—everyone makes mistakes.

Send a test email to yourself and maybe a colleague.
Check personalization: Make sure names, companies, and custom fields show up right.
Preview segments: Double-check who’s actually included before launching a campaign.

Wrapping Up: Keep It Simple

You don’t need to build a crazy complicated system to get value out of Mailscale. Start with a clean import, a handful of useful segments, and a tagging system you understand. Iterate as you go. If something’s not working, simplify.

Remember: the best email lists are the ones you actually use. Don’t get lost in the weeds—get your contacts in, get them sorted, and get on with your real work.