Importing a Subscriber List Without Creating Duplicates
A practical walkthrough of bringing an existing subscriber list into the email app — separate from campaign contacts, and worth doing carefully the first time.
If you're moving to the email app from another tool, or consolidating a list that's lived in a spreadsheet, importing subscribers is your starting point — and it's worth doing deliberately, since a messy first import is the kind of thing that quietly causes duplicate sends and confused reporting for months afterward.
Subscribers are their own list, not campaign contacts
Worth stating up front: subscriber import is a separate flow from where a campaign's audience comes from. Subscribers you import here live in the email app's own subscriber list, used for newsletters and automations you send directly through this app. That's a distinct data source from the contacts a campaign wizard pulls in for other purposes — don't assume importing subscribers here populates every audience list you'll see elsewhere in the app.
Preparing your list before you import
The cleanest imports start with a list that's already been de-duplicated on your end — a CSV with one row per real subscriber, using consistent email formatting (no stray whitespace, consistent casing). Email address is the natural key for identifying who's already in your system, so the more consistent your source data is on that field, the fewer surprises you'll run into.
If your source list has subscribers tagged by segment — VIP customers, a specific product interest, a region — carrying those tags into the import (where your source format supports it) means you can immediately target automations and campaigns at the right subset, rather than re-segmenting from scratch after the fact.
Running the import
The import goes through the app's own /api/subscribers/import route, which is a straightforward "hand it your list, get back a result" flow. Run a small batch first if you're importing a large or unfamiliar list — a few dozen rows — and check that the result looks right (the count matches what you expected, tags came through correctly) before you commit to importing the full list in one pass.
Avoiding duplicates on repeat imports
The scenario worth planning for isn't your first import — it's your second one, weeks later, when your source list has grown and you need to bring in only what's new. Re-importing an entire list from scratch every time you have new subscribers is the path that risks duplicates if the underlying matching isn't doing exactly what you expect. Where possible, export only the new or changed rows from your source system rather than the full list, and treat a full re-import as something to verify carefully rather than run as routine maintenance.
After the import
Once subscribers are in, they're available to target in your automations and campaigns the same as any subscriber who joined through a signup form. Spot-check a few imported records to confirm names, tags, and email addresses landed the way you expected before you build a campaign or automation around the freshly imported list — catching a formatting issue before your first send is considerably less costly than catching it after.